# Math Help - Simple Differentiation..

1. ## Simple Differentiation..

Thank you in advanced for your help. This is "urgent" since i am need to leave soon <.<...

I did not catch on right away for this topic. If you can help I'd appreciate it.

If y=x^3 +2x, and dx/dt=5, find dy/dt when x=2

and

If z^2=X^2+y^2, dx/dt=2, and dy/dt=3, find dz/dt when x=5 and y=12.

2. $y = x^3 + 2x$

$\frac{dy}{dt} = 3x^{2} \frac{dx}{dt} + 2 \frac{dx}{dt}$

same process for other one.

3. hmm alright.
I got them both thank you =).

4. Erm... how about a question like "A man starts walking north at 4ft/s from point P. Five minutes lare a women starts walking south at 5ft/s from a point 500ft Due east of P. At what rate are the people moving apart 15min after the woman starts walking?

Well i know that after 5min, the guy has walked 1200ft, and after 15min, 2600ft. and after 10 min for the woman, she would have walked 3000 feet...

I am guessing i need to use x^2+y^2 = r^2 but i am not sure how..