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Re: If f(2x - 1) = 4x² - 4x - 8, then f(5) =
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12 Aug 2018, 07:24

GMATPrepNow wrote:

If f(2x - 1) = 4x² - 4x - 8, then f(5) =

A) 16 B) 18 C) 36 D) 48 E) 72

Another way.. May help in such questions somewhere else..

If you look at the equation, you can easily convert the equation ... \(f(2x-1)=4x^2-4x-8=4x^2-4x+1-9=(2x-1)^2-9\) So it can be literally written as \(f(x)=x^2-9\), So f (5)=5^2-9=25-9=16
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