ISEE Upper Level Math : How to divide variables

Study concepts, example questions & explanations for ISEE Upper Level Math

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Example Questions

Example Question #221 : Algebraic Concepts

Divide:

\(\displaystyle \frac{-4x^{4}-6x^{3}+8x^{2}}{2x^{2}}\)

Possible Answers:

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

\(\displaystyle -6x^{2}-8x+10\)

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

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

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

Correct answer:

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

Explanation:

To divide this problem we start by simplify it. In this problem we can break the large fraction into three smaller fractions.

\(\displaystyle \frac{-4x^{4}-6x^{3}+8x^{2}}{2x^{2}}=\frac{-4x^{4}}{2x^{2}}-\frac{6x^{3}}{2x^{2}}+\frac{8x^{2}}{2x^{2}}\)

From here we can factor out a \(\displaystyle 2x^2\) from the numerator and denominator of each fraction.

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

Now we can cancel the \(\displaystyle 2x^2\) terms and are left with the following result:

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

Example Question #11 : How To Divide Variables

Simplify the following expression:

\(\displaystyle \frac{343w^7}{49w^3}\)

Possible Answers:

\(\displaystyle \frac{49w^7}{w^3}\)

\(\displaystyle 7w^4\)

\(\displaystyle 343w^4\)

\(\displaystyle \frac{343w^4}{49}\)

Correct answer:

\(\displaystyle 7w^4\)

Explanation:

Simplify the following expression:

\(\displaystyle \frac{343w^7}{49w^3}\)

Let's begin by simplifying the coefficients

\(\displaystyle \frac{343w^7}{49w^3}=\frac{49*7w^7}{49w^3}=\frac{7w^7}{w^3}\)

Next, complete the question by subtracting the exponents:

\(\displaystyle \frac{7w^7}{w^3}=7w^{7-3}=7w^4\)

So, our answer is:

\(\displaystyle 7w^4\)

Example Question #221 : Algebraic Concepts

Simplify the following expression:

\(\displaystyle \frac{49x^3y^5b^{12}}{7x^2y^6b^{8}}\)

Possible Answers:

\(\displaystyle \frac{7x^2b^4}{y}\)

\(\displaystyle 7xb^4y\)

\(\displaystyle \frac{49xb^4}{7y}\)

\(\displaystyle \frac{7xb^4}{y}\)

Correct answer:

\(\displaystyle \frac{7xb^4}{y}\)

Explanation:

Simplify the following expression:

\(\displaystyle \frac{49x^3y^5b^{12}}{7x^2y^6b^{8}}\)

Let's begin by simplifying the coefficients:

We have a 49 on top and a 7 on bottom. We can treat this just like a regular fraction:

\(\displaystyle \frac{49}{7}=7\)

Next, to deal with our variables, all we need to do is subtract the bottom exponent from the top exponent. If we get a negative number, we just put that number on the bottom.

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

\(\displaystyle y^{5-6}=y^{-1}=\frac{1}{y}\)

\(\displaystyle b^{12-8}=b^4\)

So our answer will look like this:

\(\displaystyle \frac{7xb^4}{y}\)

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