I'm having difficulties in obtaining the book/calculator answer to the function(adsbygoogle = window.adsbygoogle || []).push({});

f(x) = (x-1)(x+5) when f(1/x).

The book answer is: [(1-a)(1+5a)]/a

The answer I get is: 1/(a^2) + 4a - 5

. or : (1 + 4a - 5a^2)/a^2

. or : [(1 + 4a)/a^2] - 5

I know that all these answers are possible answers, but I can't for the life of me figure out how the book got the answer (I've also checked with a graphing calculator, and recieved the same answers)

- Thanks :)

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# Homework Help: F(x)=(x-1)(x+5) when f(1/x)

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