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( x + 5 ) ( x 5 ) = x 2 25 ( x + 11 ) ( x 11 ) = x 2 121 ( 2 x + 3 ) ( 2 x 3 ) = 4 x 2 9

Because the sign changes in the second binomial, the outer and inner terms cancel each other out, and we are left only with the square of the first term minus the square of the last term.

Is there a special form for the sum of squares?

No. The difference of squares occurs because the opposite signs of the binomials cause the middle terms to disappear. There are no two binomials that multiply to equal a sum of squares.

Difference of squares

When a binomial is multiplied by a binomial with the same terms separated by the opposite sign, the result is the square of the first term minus the square of the last term.

( a + b ) ( a b ) = a 2 b 2

Given a binomial multiplied by a binomial with the same terms but the opposite sign, find the difference of squares.

  1. Square the first term of the binomials.
  2. Square the last term of the binomials.
  3. Subtract the square of the last term from the square of the first term.

Multiplying binomials resulting in a difference of squares

Multiply ( 9 x + 4 ) ( 9 x 4 ) .

Square the first term to get ( 9 x ) 2 = 81 x 2 . Square the last term to get 4 2 = 16. Subtract the square of the last term from the square of the first term to find the product of 81 x 2 16.

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Multiply ( 2 x + 7 ) ( 2 x 7 ) .

4 x 2 −49

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Performing operations with polynomials of several variables

We have looked at polynomials containing only one variable. However, a polynomial can contain several variables. All of the same rules apply when working with polynomials containing several variables. Consider an example:

( a + 2 b ) ( 4 a b c ) a ( 4 a b c ) + 2 b ( 4 a b c ) Use the distributive property . 4 a 2 a b a c + 8 a b 2 b 2 2 b c Multiply . 4 a 2 + ( a b + 8 a b ) a c 2 b 2 2 b c Combine like terms . 4 a 2 + 7 a b a c 2 b c 2 b 2 Simplify .

Multiplying polynomials containing several variables

Multiply ( x + 4 ) ( 3 x 2 y + 5 ) .

Follow the same steps that we used to multiply polynomials containing only one variable.

x ( 3 x 2 y + 5 ) + 4 ( 3 x 2 y + 5 )   Use the distributive property . 3 x 2 2 x y + 5 x + 12 x 8 y + 20 Multiply . 3 x 2 2 x y + ( 5 x + 12 x ) 8 y + 20 Combine like terms . 3 x 2 2 x y + 17 x 8 y + 20   Simplify .
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Multiply ( 3 x 1 ) ( 2 x + 7 y 9 ) .

6 x 2 + 21 x y −29 x −7 y + 9

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Access these online resources for additional instruction and practice with polynomials.

Key equations

perfect square trinomial ( x + a ) 2 = ( x + a ) ( x + a ) = x 2 + 2 a x + a 2
difference of squares ( a + b ) ( a b ) = a 2 b 2

Key concepts

  • A polynomial is a sum of terms each consisting of a variable raised to a non-negative integer power. The degree is the highest power of the variable that occurs in the polynomial. The leading term is the term containing the highest degree, and the leading coefficient is the coefficient of that term. See [link] .
  • We can add and subtract polynomials by combining like terms. See [link] and [link] .
  • To multiply polynomials, use the distributive property to multiply each term in the first polynomial by each term in the second. Then add the products. See [link] .
  • FOIL (First, Outer, Inner, Last) is a shortcut that can be used to multiply binomials. See [link] .
  • Perfect square trinomials and difference of squares are special products. See [link] and [link] .
  • Follow the same rules to work with polynomials containing several variables. See [link] .

Section exercises

Verbal

Evaluate the following statement: The degree of a polynomial in standard form is the exponent of the leading term. Explain why the statement is true or false.

The statement is true. In standard form, the polynomial with the highest value exponent is placed first and is the leading term. The degree of a polynomial is the value of the highest exponent, which in standard form is also the exponent of the leading term.

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Many times, multiplying two binomials with two variables results in a trinomial. This is not the case when there is a difference of two squares. Explain why the product in this case is also a binomial.

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You can multiply polynomials with any number of terms and any number of variables using four basic steps over and over until you reach the expanded polynomial. What are the four steps?

Use the distributive property, multiply, combine like terms, and simplify.

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State whether the following statement is true and explain why or why not: A trinomial is always a higher degree than a monomial.

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Algebraic

For the following exercises, identify the degree of the polynomial.

14 m 3 + m 2 16 m + 8

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200 p 30 p 2 m + 40 m 3

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6 y 4 y 5 + 3 y 4

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For the following exercises, find the sum or difference.

( 12 x 2 + 3 x ) ( 8 x 2 −19 )

4 x 2 + 3 x + 19

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( 4 z 3 + 8 z 2 z ) + ( −2 z 2 + z + 6 )

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( 6 w 2 + 24 w + 24 ) ( 3 w 2 6 w + 3 )

3 w 2 + 30 w + 21

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( 7 a 3 + 6 a 2 4 a 13 ) + ( 3 a 3 4 a 2 + 6 a + 17 )

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( 11 b 4 6 b 3 + 18 b 2 4 b + 8 ) ( 3 b 3 + 6 b 2 + 3 b )

11 b 4 −9 b 3 + 12 b 2 −7 b + 8

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( 49 p 2 25 ) + ( 16 p 4 32 p 2 + 16 )

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For the following exercises, find the product.

( 4 x + 2 ) ( 6 x 4 )

24 x 2 −4 x −8

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( 14 c 2 + 4 c ) ( 2 c 2 3 c )

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( 6 b 2 6 ) ( 4 b 2 4 )

24 b 4 −48 b 2 + 24

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( 3 d 5 ) ( 2 d + 9 )

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( 9 v 11 ) ( 11 v 9 )

99 v 2 −202 v + 99

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( 4 t 2 + 7 t ) ( −3 t 2 + 4 )

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( 8 n 4 ) ( n 2 + 9 )

8 n 3 −4 n 2 + 72 n −36

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For the following exercises, expand the binomial.

( 3 y 7 ) 2

9 y 2 −42 y + 49

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( 4 p + 9 ) 2

16 p 2 + 72 p + 81

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( 3 y 6 ) 2

9 y 2 −36 y + 36

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For the following exercises, multiply the binomials.

( 4 c + 1 ) ( 4 c 1 )

16 c 2 −1

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( 9 a 4 ) ( 9 a + 4 )

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( 15 n 6 ) ( 15 n + 6 )

225 n 2 −36

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( 25 b + 2 ) ( 25 b 2 )

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( 4 + 4 m ) ( 4 4 m )

−16 m 2 + 16

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( 14 p + 7 ) ( 14 p 7 )

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( 11 q 10 ) ( 11 q + 10 )

121 q 2 −100

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For the following exercises, multiply the polynomials.

( 2 x 2 + 2 x + 1 ) ( 4 x 1 )

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( 4 t 2 + t 7 ) ( 4 t 2 1 )

16 t 4 + 4 t 3 −32 t 2 t + 7

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( x 1 ) ( x 2 2 x + 1 )

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( y 2 ) ( y 2 4 y 9 )

y 3 −6 y 2 y + 18

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( 6 k 5 ) ( 6 k 2 + 5 k 1 )

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( 3 p 2 + 2 p 10 ) ( p 1 )

3 p 3 p 2 −12 p + 10

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( 4 m 13 ) ( 2 m 2 7 m + 9 )

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( a + b ) ( a b )

a 2 b 2

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( 4 x 6 y ) ( 6 x 4 y )

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( 4 t 5 u ) 2

16 t 2 −40 t u + 25 u 2

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( 9 m + 4 n 1 ) ( 2 m + 8 )

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( 4 t x ) ( t x + 1 )

4 t 2 + x 2 + 4 t −5 t x x

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( b 2 1 ) ( a 2 + 2 a b + b 2 )

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( 4 r d ) ( 6 r + 7 d )

24 r 2 + 22 r d −7 d 2

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( x + y ) ( x 2 x y + y 2 )

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Real-world applications

A developer wants to purchase a plot of land to build a house. The area of the plot can be described by the following expression: ( 4 x + 1 ) ( 8 x 3 ) where x is measured in meters. Multiply the binomials to find the area of the plot in standard form.

32 x 2 −4 x −3 m 2

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A prospective buyer wants to know how much grain a specific silo can hold. The area of the floor of the silo is ( 2 x + 9 ) 2 . The height of the silo is 10 x + 10 , where x is measured in feet. Expand the square and multiply by the height to find the expression that shows how much grain the silo can hold.

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Extensions

For the following exercises, perform the given operations.

( 4 t 7 ) 2 ( 2 t + 1 ) ( 4 t 2 + 2 t + 11 )

32 t 3 100 t 2 + 40 t + 38

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( 3 b + 6 ) ( 3 b 6 ) ( 9 b 2 36 )

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( a 2 + 4 a c + 4 c 2 ) ( a 2 4 c 2 )

a 4 + 4 a 3 c −16 a c 3 −16 c 4

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Questions & Answers

Ayele, K., 2003. Introductory Economics, 3rd ed., Addis Ababa.
Widad Reply
can you send the book attached ?
Ariel
?
Ariel
What is economics
Widad Reply
the study of how humans make choices under conditions of scarcity
AI-Robot
U(x,y) = (x×y)1/2 find mu of x for y
Desalegn Reply
U(x,y) = (x×y)1/2 find mu of x for y
Desalegn
what is ecnomics
Jan Reply
this is the study of how the society manages it's scarce resources
Belonwu
what is macroeconomic
John Reply
macroeconomic is the branch of economics which studies actions, scale, activities and behaviour of the aggregate economy as a whole.
husaini
etc
husaini
difference between firm and industry
husaini Reply
what's the difference between a firm and an industry
Abdul
firm is the unit which transform inputs to output where as industry contain combination of firms with similar production 😅😅
Abdulraufu
Suppose the demand function that a firm faces shifted from Qd  120 3P to Qd  90  3P and the supply function has shifted from QS  20  2P to QS 10  2P . a) Find the effect of this change on price and quantity. b) Which of the changes in demand and supply is higher?
Toofiq Reply
explain standard reason why economic is a science
innocent Reply
factors influencing supply
Petrus Reply
what is economic.
Milan Reply
scares means__________________ends resources. unlimited
Jan
economics is a science that studies human behaviour as a relationship b/w ends and scares means which have alternative uses
Jan
calculate the profit maximizing for demand and supply
Zarshad Reply
Why qualify 28 supplies
Milan
what are explicit costs
Nomsa Reply
out-of-pocket costs for a firm, for example, payments for wages and salaries, rent, or materials
AI-Robot
concepts of supply in microeconomics
David Reply
economic overview notes
Amahle Reply
identify a demand and a supply curve
Salome Reply
i don't know
Parul
there's a difference
Aryan
Demand curve shows that how supply and others conditions affect on demand of a particular thing and what percent demand increase whith increase of supply of goods
Israr
Hi Sir please how do u calculate Cross elastic demand and income elastic demand?
Abari
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Source:  OpenStax, Algebra and trigonometry. OpenStax CNX. Nov 14, 2016 Download for free at https://legacy.cnx.org/content/col11758/1.6
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