PSAT Math : How to subtract exponents

Study concepts, example questions & explanations for PSAT Math

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Example Questions

Example Question #100 :Exponents

Ifmandnare integers such thatm<n< 0 andm2n2= 7, which of the following can be the value ofm+n?

I. –5

II. –7

III. –9

Possible Answers:

I and II only

II only

I only

I, II and III only

II and III only

Correct answer:

II only

Explanation:

mandnare both less than zero and thus negative integers, giving usm2andn2as perfect squares. The only perfect squares with a difference of 7 is 16 – 9, therefore m = –4 and n = –3.

Example Question #1 :How To Subtract Exponents

Possible Answers:

Correct answer:

Explanation:

To simplify, we can rewrite the numerator using a common exponential base.

Now, we can factor out the numerator.

The eights cancel to give us our final answer.

Example Question #1 :How To Subtract Exponents

If, then what is?

Possible Answers:

Correct answer:

Explanation:

Follow the order of operations by solving the expression within the parentheses first.

Return to solve the original expression.

Example Question #3 :How To Subtract Exponents

Solve:

Possible Answers:

Correct answer:

Explanation:

Subtract the denominator exponent from the numerator's exponent, since they have the same base.

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