1. ## deriv inverse fn?

Let f(x) = x^3+x. If h is the inverse function of f then h'(2)=
a. 1/13
b.1/4
c. 1
d.4
e. 13

2. ## Ok

Originally Posted by sandiego234
Let f(x) = x^3+x. If h is the inverse function of f then h'(2)=
a. 1/13
b.1/4
c. 1
d.4
e. 13
here is my favorite way of doing it....we have $y=x^3+x$...now to get the inverse we switch and solve back for y...but what if we did this....we say = $x=y^3+y$...then we say $\frac{dx}{dy}=3y^2+1$...therfore $\frac{dy}{dx}=\frac{1}{3y^2+1}$...therefore...we would get $\frac{1}{13}$