# Homework Help: Rate of change calculus?

1. Jul 21, 2011

### homeylova223

Hello everyone I have a two question

my first one is differentiate with respect to t

y=x^2-3x find dy/dt when x=3 and dx/dt=2

This is what I did
dy/dt=2x dx/dt (I am stuck right here)

my second one is

xy=4 find dy/dt when x=8 dx/dt=10

2. Jul 21, 2011

### MisterX

What is the derivative of -3x with respect to t, in terms of dx/dt?

First, solve for y, using the first equation. Then get dy/dt in terms of x and dx/dt using the chain rule.