Question

A point moves along the curve y= x^2+1 in such way that when x=4 the x-coordinate is increasing at the rate of 5ft/sec at what rate is the y coordinate changing at that time?

Answer 1

`40ft`/s`ec`

Explanation:

`y=x^2+1`, Differentiating implicitly with respect to t.....

`dy/dt=2xdx/dt+0`. When `x=4, dy/dt=2[4]dx/dt`

So `dy/dt=8dx/dt`. we are told `dx/dt=`5ft`/sec` .........and so `dy/dt=40ft`/sec.