Simplify difference quotient involving difference of cubes

Question: How to simplify 2(h+1)^3 - 2 all over h ?
I am doing a function f(x) = 2x^3 on [1, 1 + h]Assuming I'm correct, that would be f(x+h) - f(x) over htherefor, (2(h+1)^3) - (2(1)^3) over hwhich simplifies to 2(h+1)^3 -2 over hHowever, I am being told the correct answer is 2(h+1)^3 -1 over hWhat did I do wrong here?

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Answered By:

Doug C.
Math Tutor with Reputation to make difficult concepts understandable

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Written Explanation:

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