Algebra 1 : How to divide trinomials

Study concepts, example questions & explanations for Algebra 1

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Example Questions

Example Question #1 : How To Divide Trinomials

Divide:

\displaystyle \frac{3x^2+3x-6}{3x+6}

Possible Answers:

\displaystyle -6

\displaystyle 3

\displaystyle x+2

\displaystyle x-1

Correct answer:

\displaystyle x-1

Explanation:

Factor the numerator and denominator:

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

Cancel the factors that appear in both the numerator and the denominator:

\displaystyle \frac{3(x+2)(x-1)}{3(x+2)}=\frac{x-1}{1}=x-1

Example Question #2 : How To Divide Trinomials

Divide the following trinomials:  \displaystyle \frac{x^2-6x+9}{x^2+5x-24}

Possible Answers:

\displaystyle -\frac{3}{8}

\displaystyle -\frac{6}{5}

\displaystyle \frac{x+3}{x-8}

\displaystyle \frac{x-3}{x+8}

\displaystyle \frac{1}{x+8}

Correct answer:

\displaystyle \frac{x-3}{x+8}

Explanation:

In order to divide, we must first factor both trinomials on the numerator and denominator.

\displaystyle \frac{x^2-6x+9}{x^2+5x-24} = \frac{(x-3)(x-3)}{(x-3)(x+8)}

Notice that we now have common terms in the numerator and denominator that can be divided and cancelled.  

Cancel the \displaystyle x-3 terms in the numerator and denominator.

The answer is:  \displaystyle \frac{x-3}{x+8}

Example Question #1 : How To Divide Trinomials

Divide the trinomials:  \displaystyle \frac{x^2-3x+2}{x^2+9x-10}

Possible Answers:

\displaystyle \frac{1}{5}

\displaystyle -\frac{1}{5}

\displaystyle \frac{x+2}{x-10}

\displaystyle \frac{x-2}{x+10}

Correct answer:

\displaystyle \frac{x-2}{x+10}

Explanation:

In order to simplify this, we will need to factorize the numerator and denominator.

\displaystyle x^2-3x+2 = (x-1)(x-2)

\displaystyle x^2+9x-10 =(x-1)(x+10)

Then, \displaystyle \frac{x^2-3x+2}{x^2+9x-10}= \frac{(x-1)(x-2)}{(x-1)(x+10)}.

Simplify the common terms in the numerator and denominator.

The answer is:  \displaystyle \frac{x-2}{x+10}

Example Question #2 : How To Divide Trinomials

Divide the trinomials:  \displaystyle \frac{x^2+4x-12}{x^2-x-42}

Possible Answers:

\displaystyle 3x+30

\displaystyle \frac{x+2}{x-7}

\displaystyle \frac{4x-12}{42-x}

\displaystyle \frac{x-2}{x+7}

\displaystyle \frac{x-2}{x-7}

Correct answer:

\displaystyle \frac{x-2}{x-7}

Explanation:

Factor both trinomials on the top of the numerator and denominator.

\displaystyle \frac{x^2+4x-12}{x^2-x-42} = \frac{(x+6)(x-2)}{(x+6)(x-7)}

Notice that both the top and bottom share the \displaystyle x+6 term, which can be eliminated.

The answer is:  \displaystyle \frac{x-2}{x-7}

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