How to simplify 2(h+1)^3 - 2 all over h ?

Question

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 h

therefor, (2(h+1)^3) - (2(1)^3) over h

which simplifies to 2(h+1)^3 -2 over h

However, I am being told the correct answer is 2(h+1)^3 -1 over h

What did I do wrong here?

Answer 1

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