Thread: inverse function derivative

find the value of d/dx(f^-1(x)) at x=2 when f(x)=2x-4
(a)3
(b)1/3
(c)1/2
(d)1/6

my answer :1/2

Originally Posted by gracy

find the value of d/dx(f^-1(x)) at x=2 when f(x)=2x-4
(a)3
(b)1/3
(c)1/2
(d)1/6

my answer :1/2

Yes, 1/2 is correct.

That is easy.
How come you were asking for the inverse of a cubic function before? That one is super hard. You have to use the Cubic Formula there.
For Linear and Quadratic functions, getting their inverses, if they exist, is relatively easy.

Originally Posted by gracy

find the value of d/dx(f^-1(x)) at x=2 when f(x)=2x-4
(a)3
(b)1/3
(c)1/2
(d)1/6

my answer :1/2

Hello, Gracy,

your answer is correct.

f is a linear function therefore the inverse of f is a linear function too:

. The derivative of this function is a constant: 1/2.

EB