Find the intervals on which the function is increasing and decreasing.
y= x^(1/4) (x+4)
I took the derivative of the function, it is (1/4)x^(-3/4)
that's all I know.
That's not the derivative. What happened to the (x+4)?
Once you find the derivative, where is it positive? That's where the function is increasing. Confusion on this point is not encouraging. It is a fundamental property of the derivative. You would do well to back up and re-read a few chapters.