Find the inverse of the function #f(x)= -5x# How would I do this?

Redirected from "Suppose that I don't have a formula for #g(x)# but I know that #g(1) = 3# and #g'(x) = sqrt(x^2+15)# for all x. How do I use a linear approximation to estimate #g(0.9)# and #g(1.1)#?"
1 Answer
Dec 27, 2017

#f^-1(x)=-x/5#

Explanation:

Replace #f(x)# with #y#

#y=-5x#

Replace #y# with #x# and vice versa:

#x=-5y#

Solve for #y#:

#-x/5=y# (Divide by #-5# to isolate #y#)

#y=-x/5# (Rewrite so that #y# is the subject of the equation)

#therefore f^-1(x)=-x/5#