Supposedly Simple Derivatives

[eyesofumbrage]

Most of the time I can at least pinpoint what I don't understand about a math problem, but this time I'm so in the dark it's frustrating. What makes it worse is that it's the simplest problem on the worksheet! I have both the problem and the answer. It's getting from one to the other that's got me stumped. Here's the problem I'm stuck on:

find f'(x) when f(x) = (x^2 - 4x)/sqroot x

The answer is (3x - 4)/(2x^1/2)

I'm hoping someone can help me attack this one. I won't be able to sleep until it's conquered.

 

[racuna]

You need to apply the quotient rule.
fg'-gf'/g^2

Your (x^2-4x) is f and sqrt(x) is g.

Set the bottom (sqrt(x)) to x^(1/2), where you can apply the general power rule to that part. Hope this helps!