College Algebra : Rational Expressions

Study concepts, example questions & explanations for College Algebra

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Example Questions

Example Question #371 : College Algebra

Rationalize the following fraction:

\(\displaystyle \frac{15}{\sqrt{5}}\)

Possible Answers:

\(\displaystyle 3\sqrt{5}\)

\(\displaystyle 15\sqrt{5}\)

\(\displaystyle 5\sqrt{3}\)

\(\displaystyle \frac{3\sqrt{5}}{5}\)

Correct answer:

\(\displaystyle 3\sqrt{5}\)

Explanation:

Rationalize the following fraction:

\(\displaystyle \frac{15}{\sqrt{5}}\)

To rationalize a denominator, we will multiply the top and bottom of the fraction by the denominator.

\(\displaystyle \frac{15}{\sqrt{5}}*\frac{\sqrt{5}}{\sqrt{5}}=\frac{15\sqrt{5}}{(\sqrt{5})^2}=\frac{15\sqrt{5}}{5}=3\sqrt{5}\)

And we have our answer

Example Question #92 : Review And Other Topics

Simplify the following:

 \(\displaystyle \frac{x^{2}-9}{x^{2}-x-12}\)

Possible Answers:

\(\displaystyle \frac{x-3}{x+4}\)

\(\displaystyle \frac{x+3}{x-4}\)

\(\displaystyle \frac{x-3}{x-4}\)

\(\displaystyle \frac{x+3}{x+4}\)

\(\displaystyle \frac{x-2}{x-4}\)

Correct answer:

\(\displaystyle \frac{x-3}{x-4}\)

Explanation:

First we need to factor both polynomials.

\(\displaystyle \frac{x^{2}-9}{x^{2}-x-12}\)

Becomes

 

\(\displaystyle \frac{(x+3)(x-3)}{(x+3)(x-4)}\)

 

Now we cancel out any variables that are in BOTH the numerator and denominator. Remember that if a group of variables/numbers are inside parenthesis, they are considered a single term.

The common term in this case is \(\displaystyle (x+3)\), removing that from the equation gives us

 

\(\displaystyle \frac{x-3}{x-4}\)

 

Example Question #93 : Review And Other Topics

Simplify the following

\(\displaystyle \frac{2b^{2}+7b+5}{b^{2}-1}\)

Possible Answers:

\(\displaystyle \frac{2b+5}{b-1}\)

\(\displaystyle \frac{b+5}{b-1}\)

\(\displaystyle \frac{2b+5}{b+1}\)

\(\displaystyle \frac{2b-5}{b-1}\)

\(\displaystyle \frac{2b-5}{b+1}\)

Correct answer:

\(\displaystyle \frac{2b+5}{b-1}\)

Explanation:

The first step is to factor both polynomials:

\(\displaystyle \frac{2b^{2}+7b+5}{b^{2}-1}\)  Becomes \(\displaystyle \frac{(2b+5)(b+1)}{(b+1)(b-1)}\)

 

Now we cancel out any terms that are in both the numerator and denominator. Remember that any variables/numbers that are in parenthesis are considered a single term.

In this case, the common term is \(\displaystyle (b+1)\)

Once we remove that, we are left with:

\(\displaystyle \frac{2b+5}{b-1}\)

 

Example Question #92 : Review And Other Topics

Simplify the following:

\(\displaystyle \frac{x^{2}-2x-8}{x^{2}-x-12}\)

Possible Answers:

\(\displaystyle \frac{x-2}{x-3}\)

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

\(\displaystyle \frac{x^{2}}{x+3}\)

\(\displaystyle \frac{x+2}{x+3}\)

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

Correct answer:

\(\displaystyle \frac{x+2}{x+3}\)

Explanation:

The first step is to factor both polynomials

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

 

Now we cancel out any terms that are in both the numerator and denominator. Remember that any variables/numbers that are in parenthesis are considered a single term.

In this case, the common term is \(\displaystyle (x-4)\)

 

Simplified, the equation is:

\(\displaystyle \frac{x+2}{x+3}\)

Example Question #372 : College Algebra

Simplify the following:

\(\displaystyle \frac{3x^{2}+11x+10}{3x^{2}-x-10}\)

Possible Answers:

\(\displaystyle \frac{3x+5}{x-2}\)

\(\displaystyle \frac{x+2}{3x+5}\)

\(\displaystyle \frac{x-2}{x+2}\)

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

\(\displaystyle \frac{x+2}{x-2}\)

Correct answer:

\(\displaystyle \frac{x+2}{x-2}\)

Explanation:

The first step is to factor both polynomials

 

\(\displaystyle \frac{3x^{2}+11x+10}{3x^{2}-x-10}\) becomes \(\displaystyle \frac{(3x+5)(x+2)}{(3x+5)(x-2)}\)

 

Now we cancel out any terms that are in both the numerator and denominator. Remember that any variables/numbers that are in parenthesis are considered a single term.

In this case, the common term is \(\displaystyle (3x+5)\)

Simplified, the equation is:

\(\displaystyle \frac{x+2}{x-2}\)

Example Question #1 : Rational Expressions

Simplify the following:

\(\displaystyle \frac{16x^{2}-9}{4x^{2}-17x-15}\)

Possible Answers:

\(\displaystyle \frac{(x-5)}{(4x-3)}\)

\(\displaystyle \frac{(4x+3)}{(x+5)}\)

\(\displaystyle \frac{(4x+3)}{(x-5)}\)

\(\displaystyle \frac{(4x-3)}{(x+5)}\)

\(\displaystyle \frac{(4x-3)}{(x-5)}\)

Correct answer:

\(\displaystyle \frac{(4x-3)}{(x-5)}\)

Explanation:

The first step is to factor both polynomials

\(\displaystyle \frac{16x^{2}-9}{4x^{2}-17x-15}\)   becomes \(\displaystyle \frac{(4x-3)(4x+3)}{(4x+3)(x-5)}\)

Now we cancel out any terms that are in both the numerator and denominator. Remember that any variables/numbers that are in parenthesis are considered a single term.

In this case, the common term is \(\displaystyle (4x+3)\)

Simplified, the equation is:

\(\displaystyle \frac{(4x-3)}{(x-5)}\)

Example Question #2 : Rational Expressions

Simplify the following:

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

Possible Answers:

\(\displaystyle \frac{(x-1)}{(x-4)}\)

\(\displaystyle \frac{(x+1)}{(x+4)}\)

\(\displaystyle \frac{(x+1)}{(x-4)}\)

\(\displaystyle \frac{(x-2)}{(x+2)}\)

\(\displaystyle \frac{(x-1)}{(x+4)}\)

Correct answer:

\(\displaystyle \frac{(x+1)}{(x+4)}\)

Explanation:

The first step is to factor both polynomials

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

Now we cancel out any terms that are in both the numerator and denominator. Remember that any variables/numbers that are in parenthesis are considered a single term.

In this case, the common term is \(\displaystyle (x-1)\)


Simplified, the equation is:

\(\displaystyle \frac{(x+1)}{(x+4)}\)

Example Question #3 : Rational Expressions

Simplify the following:

\(\displaystyle \frac{12x^{2}+11x+2}{6x^{2}+x-2}\)

Possible Answers:

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

\(\displaystyle \frac{(4x+1)}{(2x-1)}\)

\(\displaystyle \frac{(4x+1)}{(3x+2)}\)

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

\(\displaystyle \frac{(4x+1)}{(3x-1)}\)

Correct answer:

\(\displaystyle \frac{(4x+1)}{(2x-1)}\)

Explanation:

The first step is to factor both polynomials

\(\displaystyle \frac{12x^{2}+11x+2}{6x^{2}+x-2}\) becomes  \(\displaystyle \frac{(3x+2)(4x+1)}{(2x-1)(3x+2)}\)

Now we cancel out any terms that are in both the numerator and denominator. Remember that any variables/numbers that are in parenthesis are considered a single term.

In this case, the common term is \(\displaystyle (3x+2)\)


Simplified, the equation is:

\(\displaystyle \frac{(4x+1)}{(2x-1)}\)

Example Question #2 : Rational Expressions

Simplify the following:

\(\displaystyle \frac{2x^{2}+x-15}{3x^{2}+4x-15}\)

Possible Answers:

\(\displaystyle \frac{(2x-5)}{(3x-5)}\)

\(\displaystyle \frac{(2x-5)}{(2x+5)}\)

\(\displaystyle \frac{(2x-5)}{(3x+5)}\)

\(\displaystyle \frac{(2x+5)}{(3x-5)}\)

\(\displaystyle \frac{(3x+5)}{(3x-5)}\)

Correct answer:

\(\displaystyle \frac{(2x-5)}{(3x-5)}\)

Explanation:

The first step is to factor both polynomials

\(\displaystyle \frac{2x^{2}+x-15}{3x^{2}+4x-15}\) becomes  \(\displaystyle \frac{(2x-5)(x+3)}{(3x-5)(x+3)}\)

 

Now we cancel out any terms that are in both the numerator and denominator. Remember that any variables/numbers that are in parenthesis are considered a single term.

In this case, the common term is \(\displaystyle (x+3)\)


Simplified, the equation is:

\(\displaystyle \frac{(2x-5)}{(3x-5)}\)

Example Question #5 : Rational Expressions

Simplify the following:

\(\displaystyle \frac{5x^{2}+31x+6}{5x^{2}-29x-6}\)

Possible Answers:

\(\displaystyle \frac{(5x+6)}{(3x-6)}\)

\(\displaystyle \frac{(x+6)}{(5x-6)}\)

\(\displaystyle \frac{(5x+6)}{(x-6)}\)

\(\displaystyle \frac{(x-6)}{(x+6)}\)

\(\displaystyle \frac{(x+6)}{(x-6)}\)

Correct answer:

\(\displaystyle \frac{(x+6)}{(x-6)}\)

Explanation:

The first step is to factor both polynomials

\(\displaystyle \frac{5x^{2}+31x+6}{5x^{2}-29x-6}\)  becomes    \(\displaystyle \frac{(5x+1)(x+6)}{(5x+1)(x-6)}\)

Now we cancel out any terms that are in both the numerator and denominator. Remember that any variables/numbers that are in parenthesis are considered a single term.

In this case, the common term is \(\displaystyle (5x+1)\)


Simplified, the equation is:

\(\displaystyle \frac{(x+6)}{(x-6)}\)

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