Algebra 1 : How to multiply binomials with the distributive property

Study concepts, example questions & explanations for Algebra 1

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Example Questions

Example Question #1 : How To Multiply Binomials With The Distributive Property

Simplify:

\(\displaystyle -5(x+15)-3x\)

Possible Answers:

\(\displaystyle 2x-75\)

\(\displaystyle -8x-75\)

None of the other answers are correct.

\(\displaystyle -8x+15\)

\(\displaystyle 2x+15\)

Correct answer:

\(\displaystyle -8x-75\)

Explanation:

First, distribute –5 through the parentheses by multiplying both terms by –5.

\(\displaystyle -5(x+15)-3x=-5x-75-3x\)

Then, combine the like-termed variables (–5x and –3x).

\(\displaystyle -5x-75-3x=-8x-75\)

Example Question #11 : Simplifying Expressions

Expand:

\(\displaystyle \frac{1}{3}(2x^2-6)(4x-\frac{2}{3})\)

Possible Answers:

\(\displaystyle 2\frac{2}{3}x^3+\frac{4}{9}x^2-8x+1\frac{1}{3}\)

\(\displaystyle -2\frac{2}{3}x^3-\frac{4}{9}x^2-8x+1\frac{1}{3}\)

\(\displaystyle 2\frac{2}{3}x^3-\frac{4}{9}x^2-8x-1\frac{1}{3}\)

\(\displaystyle 2\frac{2}{3}x^3-\frac{4}{9}x^2+8x+1\frac{1}{3}\)

\(\displaystyle 2\frac{2}{3}x^3-\frac{4}{9}x^2-8x+1\frac{1}{3}\)

Correct answer:

\(\displaystyle 2\frac{2}{3}x^3-\frac{4}{9}x^2-8x+1\frac{1}{3}\)

Explanation:

First, FOIL:

\(\displaystyle \frac{1}{3}(8x^3-\frac{4}{3}x^2-24x+\frac{12}{3})\)

Simplify:

\(\displaystyle \frac{1}{3}(8x^3-\frac{4}{3}x^2-24x+4)\)

Distribute the \(\displaystyle \frac{1}{3}\) through the parentheses:

\(\displaystyle \frac{8}{3}x^3-\frac{4}{9}x^2-\frac{24}{3}x+\frac{4}{3}\)

Rewrite to make the expression look like one of the answer choices:

\(\displaystyle 2\frac{2}{3}x^3-\frac{4}{9}x^2-8x+1\frac{1}{3}\)

Example Question #2 : How To Multiply Binomials With The Distributive Property

\(\displaystyle \textup{If }x^{2}+4x+3=0 \textup{ , what are the possible values of }x\textup{?}\)

Possible Answers:

\(\displaystyle -3, -1\)

\(\displaystyle 4, 3\)

\(\displaystyle -3, 1\)

\(\displaystyle -1, 3\)

\(\displaystyle 1,3\)

Correct answer:

\(\displaystyle -3, -1\)

Explanation:

\(\displaystyle \textup{Factor the quadratic into two binomials.}\)\(\displaystyle \, \:\left( x+a\right )\left ( x+b\right )\)

\(\displaystyle \textup{The sum of the missing numbers is the coefficient of }4x\).

\(\displaystyle \textup{The product of these numbers is the constant in the quadratic.}\)

\(\displaystyle a+b=4\:\:\:a\times b=3\:\:\textup{Therefore, }a\textup{ and }b\textup{ are 1 and 3.}\)

\(\displaystyle \left ( x+3\right )\left ( x+1\right )=0\:\:\:x= -3\textup{ or }-1\)

Example Question #1 : Quadratic Equations And Inequalities

Expand:

\(\displaystyle (4x-1)(-2x+3)\)

Possible Answers:

\(\displaystyle 8x^{2}+14x-3\)

\(\displaystyle 8x^{2}+10x-3\)

None of the other answers are correct.

\(\displaystyle -8x^{2}+14x-3\)

\(\displaystyle -8x^{2}+10x-3\)

Correct answer:

\(\displaystyle -8x^{2}+14x-3\)

Explanation:

Use the FOIL method, which stands for First, Inner, Outer, Last:

\(\displaystyle (4x)(-2x)+(4x)(3)+(-1)(-2x)+(-1)(3)\)

\(\displaystyle = -8x^2+12x+2x-3\)

\(\displaystyle =-8x^{2}+14x-3\)

 

Example Question #3 : How To Multiply Binomials With The Distributive Property

Using the distributive property, simplify the following:

\(\displaystyle 4(3x^2+5x-2)\)

Possible Answers:

\(\displaystyle 7x^2+9x-6\)

\(\displaystyle 7x^2+9x+2\)

\(\displaystyle 12x^2+20x-8\)

\(\displaystyle 12x^2+20x+8\)

\(\displaystyle 0.75x^2+0.8x-0.5\)

Correct answer:

\(\displaystyle 12x^2+20x-8\)

Explanation:

The distributive property is handy to help get rid of parentheses in expressions. The distributive property says you "distribute" the multiple to every term inside the parentheses. In symbols, the rule states that 

\(\displaystyle a(b+c)=ab+ac\)

So, using this rule, we get \(\displaystyle 4(3x^2+5x-2) =4*3x^2+4*5x-4*2) = 12x^2+20x-8\)

 

Thus we have our answer is \(\displaystyle 12x^2+20x-8\).

Example Question #4 : How To Multiply Binomials With The Distributive Property

Expand:

\(\displaystyle (x-9)(3x+2)\)

Possible Answers:

\(\displaystyle 3x^{2}-25x-18\)

\(\displaystyle 3x^{2}-29x-18\)

\(\displaystyle 3x^{2}-18x-29\)

None of the other answers

\(\displaystyle 3x^{2}-18x-25\)

Correct answer:

\(\displaystyle 3x^{2}-25x-18\)

Explanation:

To multiple these binomials, you can use the FOIL method to multiply each of the expressions individually.This will give you

\(\displaystyle (x)(3x)+(x)(2)+(-9)(3x)+(-9)(2)\)

or \(\displaystyle 3x^{2}-25x-18\).

Example Question #5 : Binomials

Multiply:  \(\displaystyle (x+9)(8-x)\)

Possible Answers:

\(\displaystyle -x^2-17x+72\)

\(\displaystyle -x^2-x+72\)

\(\displaystyle -x^2-17x-72\)

\(\displaystyle -x^2+x+72\)

\(\displaystyle x^2-x-72\)

Correct answer:

\(\displaystyle -x^2-x+72\)

Explanation:

In order to multiply the binomials, we will need to multiply each term of the first binomial with the terms of the second binomial.

\(\displaystyle (x+9)(8-x) = (x)(8)+(x)(-x)+(9)(8)+(9)(-x)\)

Simplify each term.

\(\displaystyle 8x-x^2+72-9x\)

Combine like terms and reorder the powers from highest to lowest order.

The answer is:  \(\displaystyle -x^2-x+72\)

Example Question #5 : How To Multiply Binomials With The Distributive Property

Multiply the binomials:  \(\displaystyle (3-x)(y-z)\)

Possible Answers:

\(\displaystyle 3y+3z-xy+xz\)

\(\displaystyle 3y+xz\)

\(\displaystyle 3y-3z+xy+xz\)

\(\displaystyle 3y-xy+xz\)

\(\displaystyle 3y-3z-xy+xz\)

Correct answer:

\(\displaystyle 3y-3z-xy+xz\)

Explanation:

Multiply each term of the first binomial with the terms of the second binomial.

\(\displaystyle (3)(y)+(3)(-z)+(-x)(y)+(-x)(-z)\)

Simplify the terms of this expression.

\(\displaystyle 3y-3z-xy+xz\)

There are no like terms to simplify.

The answer is:  \(\displaystyle 3y-3z-xy+xz\)

Example Question #6 : How To Multiply Binomials With The Distributive Property

Multiply:  \(\displaystyle (9-2x)(3+6x)\)

Possible Answers:

\(\displaystyle -12x^2+48x+27\)

\(\displaystyle -12x^2-48x+27\)

\(\displaystyle -12x^2-48x+12\)

\(\displaystyle -4x^2+48x+27\)

\(\displaystyle -8x^2+48x+27\)

Correct answer:

\(\displaystyle -12x^2+48x+27\)

Explanation:

Multiply each term of the first binomial with the second binomial and add the terms. 

\(\displaystyle 9(3+6x) +(-2x)(3+6x)\)

Simplify by distribution.

\(\displaystyle 27+54x-6x-12x^2\)

Combine like-terms.

\(\displaystyle 27+48x-12x^2\)

The answer is:  \(\displaystyle -12x^2+48x+27\)

Example Question #7 : How To Multiply Binomials With The Distributive Property

Simplify the following expression.

\(\displaystyle (-x+10)(3x^{2}-4)\)

Possible Answers:

\(\displaystyle 27x^{2}+4x-40\)

\(\displaystyle 3x^{3}+30x^{2}+4x+40\)

\(\displaystyle -3x^{3}+34x^{2}+40\)

None of the other answers

\(\displaystyle -3x^{3}+30x^{2}+4x-40\)

Correct answer:

\(\displaystyle -3x^{3}+30x^{2}+4x-40\)

Explanation:

\(\displaystyle (-x+10)(3x^{2}-4)\)

Use the FOIL method to multiply the binomials given.

F: \(\displaystyle -x(3x^{2})=-3x^{3}\)

O: \(\displaystyle -x(-4)=4x\)

I: \(\displaystyle 10(3x^{2})=30x^{2}\)

L: \(\displaystyle 10(-4)=-40\)

Group any like terms (none for this problem) when putting all the terms back together.

\(\displaystyle -3x^{3}+30x^{2}+4x-40\)

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