Cracking the GRE with 4 Practice Tests, 2020 Edition by The Princeton Review

Author:The Princeton Review
Language: eng
Format: epub, pdf
Publisher: Random House Children's Books
Published: 2019-08-05T16:00:00+00:00

Take a look at one more exponent problem.

If x ≠ 0 and 643 = 8x, then what is the value of x2 ?

5

6

25

36

64

Here’s How to Crack It

Solve this question by determining the value for x. To solve for x in this equation, start by rewriting the exponent expressions using a common base. Since 64 can be written as 82, the equation can be rewritten as (82)3 = 8x. Since the bases are the same, for the equation to be equal the powers have to be the same as well. (82)3 can be rewritten as 86 because of the power-multiply rule, so if 86 = 8x then x = 6. Now plug that number into the value for x2. This is now 62 which equals 36, so the correct answer is (D).

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