How do you find the inverse of #y = 5x + 20#? Precalculus Functions Defined and Notation Function Composition 1 Answer Trevor Ryan. Dec 19, 2015 #If f(x)=5x+20, then f^(-1)(x)=(x-20)/5# Explanation: By definition of the inverse function, #y=f^(-1)(x)iff f(y)=x# #iff 5y+20=x# #iff y=(x-20)/5# Answer link Related questions What is function composition? What are some examples of function composition? What are some common mistakes students make with function composition? Is function composition associative? Is it always true that #(f@g)(x) = (g@f)(x)#? If #f(x) = x + 3# and #g(x) = 2x - 7#, what is #(f@g)(x)#? If #f(x) = x^2# and #g(x) = x + 2#, what is #(f@g)(x)#? If #f(x) = x^2# and #g(x) = x + 2#, what is #(g@f)(x)#? What is the domain of #(f@g)(x)#? What is the domain of the composite function #(g@f)(x)#? See all questions in Function Composition Impact of this question 2806 views around the world You can reuse this answer Creative Commons License