## THE DISTRIBUTIVE LAW

If we desire to main point a amount by one more number, either we have the right to multiply every term that the sum by the number before we include or we can very first add the terms and then multiply. Because that example, In either case the an outcome is the same.

You are watching: Factor 2x^2+x-1

This property, which we first introduced in ar 1.8, is called the distributive law. In symbols,

a(b + c) = abdominal muscle + ac or (b + c)a = ba + ca

By applying the distributive legislation to algebraic expressions containing parentheses, we can attain equivalent expressions without parentheses.

Our very first example involves the product of a monomial and binomial.

Example 1 create 2x(x - 3) without parentheses.

Solution

We think that 2x(x - 3) together 2x and then apply the distributive regulation to obtain The above method works equally as well with the product of a monomial and trinomial.

Example 2 write - y(y2 + 3y - 4) without parentheses.

Solution

Applying the distributive home yields When simplifying expressions entailing parentheses, we very first remove the parentheses and also then integrate like terms.

Example 3 leveling a(3 - a) - 2(a + a2).

We start by remove parentheses to obtain Now, combining like terms returns a - 3a2.

We can use the distributive home to rewrite expressions in i m sorry the coefficient of one expression in parentheses is +1 or - 1.

Example 4 create each expression without parentheses.a. +(3a - 2b)b. -(2a - 3b)

Solution Notice that in example 4b, the authorize of every term is changed when the expression is created without parentheses. This is the same result that we would have obtained if we provided the measures that we presented in section 2.5 to leveling expressions.

## FACTORING MONOMIALS native POLYNOMIALS

From the symmetric building of equality, we know that if

a(b + c) = abdominal muscle + ac, then ab + ac = a(b + c)

Thus, if over there is a monomial factor usual to every terms in a polynomial, we can write the polynomial as the product of the common factor and also another polynomial. Because that instance, because each ax in x2 + 3x includes x as a factor, we have the right to write the expression as the product x(x + 3). Rewriting a polynomial in this way is called factoring, and the number x is said to it is in factored "from" or "out of" the polynomial x2 + 3x.

To aspect a monomial indigenous a polynomial:Write a set of parentheses preceded by the monomial usual to every term in the polynomial.Divide the monomial factor into each term in the polynomial and write the quotient in the parentheses.Generally, we can discover the common monomial element by inspection.

Example 1 a. 4x + 4y = 4(x + y) b. 3xy -6y - 3y(x - 2)

We can examine that we factored appropriately by multiply the factors and also verifyingthat the product is the original polynomial. Using example 1, us get If the usual monomial is difficult to find, we have the right to write every term in prime factored type and note the usual factors.

Example 2 aspect 4x3 - 6x2 + 2x.

systems We deserve to write We now see that 2x is a usual monomial factor to all 3 terms. Climate we aspect 2x out of the polynomial, and write 2x()

Now, we division each term in the polynomial by 2x and write the quotients within the parentheses come get

2x(2x2 - 3x + 1)

We can check our prize in instance 2 by multiply the factors to obtain In this book, we will certainly restrict the usual factors to monomials consist of of numerical coefficients that are integers and also to integral powers of the variables. The an option of authorize for the monomial element is a issue of convenience. Thus,

-3x2 - 6x

can it is in factored either as

-3x(x + 2) or together 3x(-x - 2)

The an initial form is usually more convenient.

Example 3Factor the end the common monomial, consisting of -1.

a. - 3x2 - 3 xyb. -x3 - x2 + x equipment Sometimes it is convenient to compose formulas in factored form.

Example 4 a. A = p + PRT = P(1 + RT) b. S = 4kR2 - 4kr2 = 4k(R2 - r2)

## 4.3BINOMIAL products I

We deserve to use the distributive law to multiply two binomials. Although there is little need to multiply binomials in arithmetic as displayed in the instance below, the distributive law additionally applies to expressions containing variables. We will now apply the over procedure because that an expression include variables.

Example 1

Write (x - 2)(x + 3) without parentheses.

Solution First, use the distributive residential or commercial property to obtain Now, incorporate like state to acquire x2 + x - 6

With practice, friend will have the ability to mentally include the 2nd and third products. Theabove procedure is sometimes referred to as the silver paper method. F, O, I, and also L was standing for: 1.The product that the very first terms.2.The product that the outer terms.3.The product the the within terms.4.The product the the critical terms.

The FOIL an approach can likewise be provided to square binomials.

Example 2

Write (x + 3)2 without parentheses.Solution

First, rewrite (x + 3)2 as (x + 3)(x + 3). Next, use the FOIL method to get Combining favor terms yieldsx2 + 6x + 9

When we have actually a monomial factor and two binomial factors, it is simplest to very first multiply the binomials.

Example 3

compose 3x(x - 2)(x + 3) there is no parentheses.Solution First, multiply the binomials come obtain3x(x2 + 3x - 2x - 6) = 3x(x2 + x - 6)

Now, apply the distributive regulation to gain 3x(x2 + x - 6) = 3x3 + 3x2 - 18x

Common Errors

Notice in instance 2 Similarly, In general, ## 4.4FACTORING TRINOMIALS ns

In ar 4.3, us saw how to discover the product of two binomials. Now we will certainly reverse this process. The is, offered the product of 2 binomials, us will find the binomial factors. The process involved is another example of factoring. Together before,we will certainly only consider factors in which the terms have integral numerical coefficients. Such determinants do not always exist, yet we will study the instances where lock do.

Consider the complying with product. Notice the the first term in the trinomial, x2, is product (1); the critical term in thetrinomial, 12, is product and the center term in the trinomial, 7x, is the sum of commodities (2) and also (3).In general, We usage this equation (from ideal to left) to factor any type of trinomial the the form x2 + Bx + C. We find two numbers whose product is C and also whose amount is B.

Example 1 variable x2 + 7x + 12.Solution we look for 2 integers whose product is 12 and also whose amount is 7. Take into consideration the complying with pairs of determinants whose product is 12. We see that the just pair of components whose product is 12 and also whose amount is 7 is 3 and 4. Thus,

x2 + 7x + 12 = (x + 3)(x + 4)

Note that once all regards to a trinomial space positive, we need only consider pairs of confident factors due to the fact that we are looking for a pair of factors whose product and sum space positive. The is, the factored hatchet of

x2 + 7x + 12would it is in of the kind

( + )( + )

When the very first and 3rd terms of a trinomial space positive yet the center term is negative, we need only consider pairs of an unfavorable factors since we are searching for a pair of determinants whose product is positive but whose amount is negative. That is,the factored type of

x2 - 5x + 6

would be of the form

(-)(-)

Example 2 factor x2 - 5x + 6.

Solution because the 3rd term is positive and also the center term is negative, we discover two negative integers who product is 6 and also whose amount is -5. We list the possibilities. We watch that the just pair of determinants whose product is 6 and whose sum is -5 is -3 and -2. Thus,

x2 - 5x + 6 = (x - 3)(x - 2)

When the first term the a trinomial is positive and also the third term is negative,the indications in the factored type are opposite. That is, the factored kind of

x2 - x - 12

would be of the type

(+)(-) or (-)(+)

Example 3

Factor x2 - x - 12.

Solution us must uncover two integers who product is -12 and also whose sum is -1. We list the possibilities. We see that the just pair of components whose product is -12 and whose amount is -1 is -4 and also 3. Thus,

x2 - x - 12 = (x - 4)(x + 3)

It is much easier to factor a trinomial fully if any kind of monimial factor usual to every term the the trinomial is factored first. Because that example, we can factor

12x2 + 36x + 24

as A monomial deserve to then it is in factored from these binomial factors. However, an initial factoring the common factor 12 native the initial expression yields

12(x2 + 3x + 2)

Factoring again, we have

12(* + 2)(x + 1)

which is stated to it is in in totally factored form. In such cases, the is not essential to aspect the numerical factor itself, the is, we do not create 12 as 2 * 2 * 3.

instance 4

variable 3x2 + 12x + 12 completely.

SolutionFirst we aspect out the 3 from the trinomial to acquire

3(x2 + 4x + 4)

Now, we element the trinomial and obtain

3(x + 2)(x + 2)

The approaches we have arisen are also valid because that a trinomial such as x2 + 5xy + 6y2.

Example 5Factor x2 + 5xy + 6y2.

Solution We find two positive factors whose product is 6y2 and also whose amount is 5y (the coefficient the x). The two components are 3y and also 2y. Thus,

x2 + 5xy + 6y2 = (x + 3y)(x + 2y)

once factoring, it is best to compose the trinomial in descending powers of x. If the coefficient that the x2-term is negative, factor out a an adverse before proceeding.

Example 6

Factor 8 + 2x - x2.

Solution We an initial rewrite the trinomial in descending strength of x to get

-x2 + 2x + 8

Now, us can element out the -1 to obtain

-(x2 - 2x - 8)

Finally, we element the trinomial to yield

-(x- 4)(x + 2)

Sometimes, trinomials room not factorable.

Example 7

Factor x2 + 5x + 12.

Solution us look for 2 integers who product is 12 and whose amount is 5. From the table in instance 1 on page 149, we watch that over there is no pair of factors whose product is 12 and whose sum is 5. In this case, the trinomial is no factorable.

Skill at factoring is commonly the an outcome of extensive practice. If possible, do the factoring procedure mentally, creating your prize directly. Friend can examine the results of a administrate by multiply the binomial factors and verifying that the product is equal to the given trinomial.

## 4.5BINOMIAL products II

In this section, we usage the procedure emerged in section 4.3 to multiply binomial components whose first-degree terms have numerical coefficients other than 1 or - 1.

Example 1

Write together a polynomial.

a. (2x - 3)(x + 1)b. (3x - 2y)(3x + y)

Solution

We first apply the FOIL method and then combine like terms. As before, if we have a squared binomial, we first rewrite it as a product, then use the foil method.

Example 2

a. (3x + 2)2 = (3x + 2)(3x + 2) = 9x2 + 6x + 6x + 4 = 9x2 + 12x + 4

b. (2x - y)2 = (2x - y)(2x - y) = 4x2 - 2xy - 2xy + y2 - 4x2 - 4xy + y2

As friend may have actually seen in ar 4.3, the product of 2 bionimals may have no first-degree hatchet in the answer.

Example 3

a. (2x - 3)(2x + 3) = 4x2 + 6x - 6x - 9 = 4x2 -9

b. (3x - y)(3x + y) - 9x2 + 3xy - 3xy - y2= 9x2 - y2

When a monomial factor and also two binomial components are being multiplied, that iseasiest to multiply the binomials first.

Example 4

Write 3x(2x - l)(x + 2) as a polynomial.

Solution We first multiply the binomials come get3x(2x2 + 4x - x - 2) = 3x(2x2 + 3x - 2)Now multiply by the monomial yields3x(2x2) + 3x(3x) + 3x(-2) = 6x3 + 9x2 - 6x

## 4.6FACTORING TRINOMIALS II

In ar 4.4 us factored trinomials of the kind x2 + Bx + C whereby the second-degree term had actually a coefficient of 1. Currently we want to prolong our factoring techniquesto trinomials that the form Ax2 + Bx + C, wherein the second-degree term has actually acoefficient various other than 1 or -1.

First, we think about a test to identify if a trinomial is factorable. A trinomial ofthe kind Ax2 + Bx + C is factorable if us can find two integers whose product isA * C and whose amount is B.

Example 1

Determine if 4x2 + 8x + 3 is factorable.

Solution We check to watch if there space two integers whose product is (4)(3) = 12 and whosesum is 8 (the coefficient the x). Consider the complying with possibilities. Since the determinants 6 and also 2 have a amount of 8, the worth of B in the trinomialAx2 + Bx + C, the trinomial is factorable.

Example 2

The trinomial 4x2 - 5x + 3 is not factorable, since the above table shows thatthere is no pair of determinants whose product is 12 and whose amount is -5. The check tosee if the trinomial is factorable can usually be done mentally.

Once us have identified that a trinomial the the type Ax2 + Bx + C is fac-torable, we continue to discover a pair of determinants whose product is A, a pair the factorswhose product is C, and an arrangement that returns the appropriate middle term. Weillustrate through examples.

Example 3

Factor 4x2 + 8x + 3.

Solution Above, we established that this polynomial is factorable. We now proceed. 1. We take into consideration all pairs of components whose product is 4. Due to the fact that 4 is positive, just positive integers should be considered. The possibilities space 4, 1 and also 2, 2.2. We consider all bag of factors whose product is 3. Due to the fact that the middle term is positive, take into consideration positive bag of determinants only. The possibilities are 3, 1. We write all feasible arrangements of the determinants as shown. 3. We choose the setup in i m sorry the sum of assets (2) and also (3) yields a center term of 8x.

Now, we take into consideration the administer of a trinomial in which the constant term is negative.

Example 4

Factor 6x2 + x - 2.

Solution First, we test to check out if 6x2 + x - 2 is factorable. Us look for two integers that havea product that 6(-2) = -12 and a amount of 1 (the coefficient that x). The integers 4 and-3 have actually a product of -12 and a amount of 1, therefore the trinomial is factorable. We nowproceed. We think about all pairs of components whose product is 6. Since 6 is positive, just positive integers need to be considered. Climate possibilities room 6, 1 and also 2, 3.We consider all bag of components whose product is -2. The possibilities room 2, -1 and also -2, 1. We create all possible arrange ments of the factors as shown.We select the arrangement in i m sorry the sum of products (2) and (3) yields a center term of x.

With practice, friend will have the ability to mentally examine the combinations and also will notneed to compose out every the possibilities. Paying attention to the indicators in the trinomialis specifically helpful because that mentally eliminating feasible combinations.

It is most basic to variable a trinomial written in descending powers of the variable.

Example 5

Factor.

a. 3 + 4x2 + 8x b. X - 2 + 6x2

Solution Rewrite each trinomial in descending strength of x and then monitor the services ofExamples 3 and also 4.

a. 4x2 + 8x + 3 b. 6x2 + x - 2

As we claimed in section 4.4, if a polynomial contains a common monomial factorin every of that is terms, us should variable this monomial native the polynomial beforelooking for other factors.

Example 6

Factor 242 - 44x - 40.

Solution We first factor 4 from each term come get

4(6x2 - 11x - 10)

We then variable the trinomial, come obtain

4(3x + 2)(2x - 5)

ALTERNATIVE an approach OF FACTORING TRINOMIALS

If the above "trial and also error" technique of factoring does not yield quick results, analternative method, which we will certainly now demonstrate using the earlier example4x2 + 8x + 3, may be helpful.

We understand that the trinomial is factorable due to the fact that we found two numbers whoseproduct is 12 and whose amount is 8. Those numbers space 2 and 6. We currently proceedand usage these numbers to rewrite 8x as 2x + 6x. We now aspect the very first two terms, 4*2 + 2x and also the last two terms, 6x + 3.A typical factor, 2x + 1, is in each term, so we can element again.This is the same result that we obtained before.

## 4.7FACTORING THE difference OF two SQUARES

Some polynomials occur so generally that that is advantageous to recognize these specialforms, which in tum enables us to straight write their factored form. Observe that In this ar we are interested in the town hall this connection from ideal to left, fromthe polynomial a2 - b2 come its factored kind (a + b)(a - b).

The difference of two squares, a2 - b2, equals the product of the sum a + b and the difference a - b.

Example 1

a. X2 - 9 = x2 - 32 = (x + 3)(x - 3) b. X2 - 16 = x2 - 42 = (x + 4)(x - 4)

Since

(3x)(3x) = 9x2

we deserve to view a binomial such as 9x2 - 4 together (3x)2 - 22 and also use the above methodto factor.

Example 2

a.9x2 - 4 = (3x)2 - 22= (3x + 2)(3x - 2)b.4y2 - 25x2 = (2y)2 - (5x)2= (2y + 5x)(2y - 5x)

As before, we always factor out a usual monomial first whenever possible.

Example 3

a.x3 - x5 = x3(l - x2) = x3(1 + x)(l - x)b.a2x2y - 16y = y(a2x2 - 16) = y<(ax)2 - 42>= y(ax - 4 )(ax + 4)

## 4.8EQUATIONS involving PARENTHESES

Often we need to solve equations in which the change occurs within parentheses. Wecan resolve these equations in the normal manner ~ we have simplified lock byapplying the distributive legislation to eliminate the parentheses.

Example 1

Solve 4(5 - y) + 3(2y - 1) = 3.

Solution We first apply the distributive regulation to get

20 - 4y + 6y - 3 = 3

Now combining choose terms and solving because that y yields

2y + 17 = 3

2y = -14

y=-l

The same an approach can be used to equations including binomial products.

Example 2

Solve (x + 5)(x + 3) - x = x2 + 1.

Solution First, we apply the FOIL technique to remove parentheses and also obtain

x2 + 8x + 15 - x = x2 + 1

Now, combining favor terms and also solving because that x yields

x2 + 7x + 15 = x2 + 1

7x = -14

x = -2

## 4.9WORD problems INVOLVING NUMBERS

Parentheses are useful in representing products in i m sorry the change is containedin one or an ext terms in any kind of factor.

Example 1

One integer is three more than another. If x to represent the smaller integer, representin regards to x

a. The bigger integer.b. Five times the smaller integer.c. Five times the bigger integer.

Solution a. X + 3b. 5x c. 5(x + 3)

Let us say we recognize the sum of 2 numbers is 10. If we represent one number byx, then the second number need to be 10 - x as argued by the complying with table. In general, if we recognize the amount of 2 numbers is 5 and x represents one number,the various other number have to be S - x.

Example 2

The amount of 2 integers is 13. If x represents the smaller sized integer, represent in termsof X

a. The bigger integer.b. Five times the smaller sized integer.c. 5 times the bigger integer.

Solution a. 13 - x b. 5x c. 5(13 - x)

The following example concerns the concept of continually integers that was consid-ered in ar 3.8.

Example 3

The difference of the squares of 2 consecutive odd integers is 24. If x representsthe smaller sized integer, represent in terms of x

a. The bigger integerb. The square that the smaller integer c. The square of the bigger integer.

Solution

a. X + 2b. X2 c. (x + 2)2

Sometimes, the math models (equations) because that word troubles involveparentheses. We can use the method outlined on page 115 to attain the equation.Then, we continue to settle the equation by an initial writing equivalently the equationwithout parentheses.

Example 4

One creature is five much more than a 2nd integer. 3 times the smaller integer plustwice the larger equates to 45. Discover the integers.

Solution

Steps 1-2 First, we write what we want to discover (the integers) as word phrases. Then, we represent the integers in terms of a variable.The smaller sized integer: x The larger integer: x + 5

Step 3 A sketch is no applicable.

Step 4 Now, we write an equation that represents the problem in the problemand get

3x + 2(x + 5) = 45

Step 5 using the distributive legislation to eliminate parentheses yields Step 6 The integers space 7 and 7 + 5 or 12.

## 4.10 APPLICATIONS

In this section, we will certainly examine number of applications of word difficulties that lead toequations that involve parentheses. When again, we will certainly follow the six steps out-lined on web page 115 when we settle the problems.

COIN PROBLEMS

The simple idea of problems involving coins (or bills) is that the worth of a numberof coins of the exact same denomination is equal to the product the the worth of a singlecoin and the total variety of coins. A table favor the one presented in the next instance is useful in fixing coin problems.

Example 1

A arsenal of coins consists of dimes and also quarters has a value of \$5.80. Thereare 16 an ext dimes 보다 quarters. How many dimes and also quarters are in the col-lection?

Solution

Steps 1-2 We very first write what we want to find as word phrases. Then, werepresent each phrase in regards to a variable.The number of quarters: x The variety of dimes: x + 16

Step 3 Next, we make a table mirroring the variety of coins and also their value. Step 4 currently we deserve to write one equation. Step 5 resolving the equation yields Step 6 There are 12 quarters and also 12 + 16 or 28 dimes in the collection.

INTEREST PROBLEMS

The straightforward idea of solving interest problems is that the quantity of interest i earnedin one year at an easy interest amounts to the product that the price of attention r and also theamount that money ns invested (i = r * p). For example, \$1000 invested for one yearat 9% yields i = (0.09)(1000) = \$90.

A table favor the one displayed in the next instance is advantageous in resolving interestproblems.

Example 2

Two investments produce an annual interest the \$320. \$1000 an ext is invested at11% than at 10%. How much is invest at every rate?

Solution

Steps 1-2 We very first write what we want to find as indigenous phrases. Then, werepresent each expression in terms of a variable. Amount invest at 10%: x Amount invest at 11%: x + 100

Step 3 Next, us make a table showing the lot of money invested, therates that interest, and the quantities of interest. Step 4 Now, we deserve to write an equation relating the interest from each in-vestment and also the total interest received. Step 5 To settle for x, very first multiply every member by 100 to obtain Step 6 \$1000 is invested at 10%; \$1000 + \$1000, or \$2000, is invested at11%.

MIXTURE PROBLEMS

The an easy idea of resolving mixture difficulties is that the amount (or value) of thesubstances being combined must same the lot (or value) the the last mixture.

A table choose the ones presented in the following instances is helpful in solvingmixture problems.

Example 3

How lot candy worth 80c a kilogram (kg) must a grocer blend through 60 kg ofcandy precious \$1 a kilogram to make a mixture precious 900 a kilogram?

Solution

Steps 1-2 We very first write what we want to find as a native phrase. Then, werepresent the expression in terms of a variable.Kilograms the 80c candy: x

Step 3 Next, us make a table reflecting the varieties of candy, the quantity of each,and the complete values of each. Step 4 We have the right to now write an equation. Step 5 solving the equation yields Step 6 The grocer need to use 60 kg that the 800 candy.

Another type of mixture difficulty is one that requires the mixture of the 2 liquids.

Example 4

How numerous quarts that a 20% systems of acid have to be included to 10 quarts the a 30%solution of mountain to acquire a 25% solution?

Solution

Steps 1-2 We an initial write what we want to discover as a indigenous phrase. Then, werepresent the expression in regards to a variable.

Number the quarts of 20% equipment to it is in added: x

Step 3 Next, us make a table or drawing showing the percent of each solu-tion, the quantity of each solution, and the quantity of pure mountain in eachsolution.  Step 4 We can now compose an equation relating the quantities of pure acid beforeand after combining the solutions. Step 5 To settle for x, very first multiply every member through 100 to obtain

20x + 30(10) = 25(x + 10)20x + 300 = 25x + 250 50 = 5x 10 = x

Step 6 add 10 quarts of 20% systems to create the wanted solution.

## CHAPTER SUMMARY

Algebraic expressions containing parentheses deserve to be created without clip byapplying the distributive law in the forma(b + c) = ab + ac

A polynomial that includes a monomial factor common to all terms in thepolynomial deserve to be created as the product of the common factor and anotherpolynomial by applying the distributive law in the formab + ac = a(b + c)

The distributive law have the right to be provided to main point binomials; the FOIL method suggeststhe four products involved. Given a trinomial the the type x2 + Bx + C, if there room two numbers, a and also b,whose product is C and also whose sum is B, then x2 + Bx + C = (x + a)(x + b) otherwise, the trinomial is no factorable.

A trinomial the the kind Ax2 + Bx + C is factorable if there are two numbers whoseproduct is A * C and whose amount is B.

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The difference of squaresa2 - b2 = (a + b)(a - b)

Equations involving parentheses can be solved in the usual way after the equationhas been rewritten equivalently there is no parentheses.