The function f is defined by f ( x ) = 8 x . For what value of x does

Question

The function f is defined by f ( x ) = 8 x . For what value of x does f ( x ) = 72 ?

Accepted Answer

Choice B is correct. Substituting 72 for f x in the given function yields 72 = 8 x . Dividing each side of this equation by 8 yields 9 = x . Therefore, f x = 72 when the value of x is 9 . Choice A is incorrect. This is the value of x for which f x = 64 , not f x = 72 . Choice C is incorrect. This is the value of x for which f x = 512 , not f x = 72 . Choice D is incorrect. This is the value of x for which f x = 640 , not f x = 72 .

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