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## Homework Statement

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!

## Homework Equations

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

## 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!!!