Finding critical numbers of function with rational exponent

[TsAmE]

Homework Statement

Find the critical numbers of the function:

F(x) = x^(4/5) (x - 4)^(2)

Homework Equations

None.

The Attempt at a Solution

I differentiated and got to (1 / 5th root of x) (x - 4)(2x + 4/5(x-4))

but I don't know how I can simplify the expression to be able to solve for the critical values of x

 

[Mark44]

Homework Statement

Find the critical numbers of the function:

F(x) = x^(4/5) (x - 4)^(2)

Homework Equations

None.

The Attempt at a Solution

I differentiated and got to (1 / 5th root of x) (x - 4)(2x + 4/5(x-4))

but I don't know how I can simplify the expression to be able to solve for the critical values of x

You're almost there. What values of x make F'(x) = 0? You have three factors, so for F'(x) to be zero, at least one of the factors must be zero.