[tex]f(x)=4x-5\to y=4x-5\ \ \ \ \ |add\ 5\ to\ both\ sides\\\\y+5=4x\ \ \ \ |divide\ both\ sides\ by\ 4\\\\x=\dfrac{y}{4}+\dfrac{5}{4}\to x=\dfrac{1}{4}y+\dfrac{5}{4}[/tex]
[tex]The\ inverse\ of\ f(x)\ is\ f^{-1}(x)[/tex]
[tex]Answer:f^{-1}(x)=\dfrac{1}{4}x+\dfrac{5}{4}[/tex]