# Math Help - differentiating function

1. ## differentiating function

Im stuck on this problem:

Differentiate the following function.

Heres what i did:

used sum rule, found the derivatives of the above terms.

for the 1st one i got square root of 7

the 2nd i got .75u^-.5

so sqrt[7]+.75u^-.5

thanks.

2. Originally Posted by Evan.Kimia
Im stuck on this problem:

Differentiate the following function.

Heres what i did:

used sum rule, found the derivatives of the above terms.

for the 1st one i got square root of 7

the 2nd i got .75u^-.5

so sqrt[7]+.75u^-.5

thanks.
You need to use the chain rule since the function $\sqrt{3u}$ is a composite function. The derivative should be $\frac{1}{3}(3u)^{\frac{-2}{3}}(3)=(3u)^{\frac{-2}{3}}$

So the derivative of $g(u)$ is just $g'(u)=\sqrt{7}+(3u)^{\frac{-2}{3}}$. You can simplify the second term to the cubed root of the square of $3u$.