posted by joe .
find the derivative of
y = sqrt(9 - 16x)
Use the chain rule. First find the derivative of the sqrt, and multiply that by the derivative of what is contained inside.
Use the chain rule. If we have y(x)=sqrt(9-16x) then
The first deriv. is (1/2)(9-16x)^(-1/2), you should be able to finish it.