Question

If f(x) = 4x – 9, what is the equation for f–1(x)?

Answer 1

f^{-1}(x) inverse of f(x)
f(x) is same as y so we can replace f(x) with y \[\huge\rm \color{ReD}{y}=4\color{blue}{x}-9\]
and then to find inverse `switch x and y`
\[\huge\rm \color{blue}{x}=4\color{red}{y}-9\]

Answer 2

now solve for y