# Derivative of this function?

• September 28th 2010, 10:43 PM
melliep
Derivative of this function?
I got:

1/2t^(-1/2)(x+14) + SQRT of x.

why is this wrong?
• September 28th 2010, 10:52 PM
Prove It
I don't know why your derivative has a $t$ in it.

$y = x^{\frac{1}{2}}(x+14)$.

$\frac{dy}{dx} = x^{\frac{1}{2}}\,\frac{d}{dx}(x + 14) + (x + 14)\,\frac{d}{dx}(x^{\frac{1}{2}})$

$= x^{\frac{1}{2}} + \frac{1}{2}(x + 14)x^{-\frac{1}{2}}$

$= \sqrt{x} + \frac{x + 14}{2\sqrt{x}}$.
• September 28th 2010, 11:02 PM
melliep
WOWWWWWWW. That was the problem. I inserted a 't' instead of 'x'. I am a smart one obviously.
Thank you.