(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

I am trying to solve this basic calculus problem, but I can't figure out the last step. It doesn't make sense to me. I know I'm just being an idiot and not thinking of it. This actually has little to do with calculus and more to do with basic algebra. Doh!

2. Relevant equations

The problems asks us to find the critical points of the function f(x) = x^3/5 * (4-x).

3. The attempt at a solution

I've gotten down to this point:

f'(x) = (3(4-x) / 5x^2/5) - x^2/5.

However, the solution to the problem goes on to this:

f'(x) = (3(4-x) - 5x) / 5x^2/5

I cannot for the life of me see how they reduced it down to that answer.

Any help would be much appreciated!!!

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# Homework Help: Very simple question. Yes, I'm stupid.

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