If 9^x − 9^(x − 1) = 216, what is the value of x?
Correct answer D. 5/2
Explanation
Take 9^(x − 1) common: 9^(x − 1)(9 − 1) = 216, so 9^(x − 1) = 27. Then 3^(2x − 2) = 3³, giving x = 5/2.
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