1. ## derivatie question

Here is the problem f(x) = sqrt(4x + 9)
then f' (x) = ?
Here is what I did:
1/2 d/dx[4x+9]^-1/2
1/(2*sqrt(4x+9))
This is where I get stuck.
Thank you!
Keith

2. Originally Posted by keith
Here is the problem f(x) = sqrt(4x + 9)
then f' (x) = ?
Here is what I did:
1/2 d/dx[4x+9]^-1/2
1/(2*sqrt(4x+9))
This is where I get stuck.
Thank you!
Keith

$
\frac{d}{dx}h(g(x)) = g'(x) h'(g(x))
$

In this case $g(x)=4x+9$ and $h(x)=\sqrt(x)$, so:

$
\frac{d}{dx}h(g(x)) =\frac{d}{dx}\sqrt(4x+9)= 4 (1/2) (4x+9)^{-1/2}=2 (4x+9)^{-1/2}
$

RonL