Question 1186177
{{{x=4-5*f^(-1)}}}

{{{x-4=-5f^(-1)}}}

{{{(x-4)/(-5)=f^(-1)}}}

{{{highlight(f^(-1)=(4-x)/5)}}}


You can now substitute 4-5x for x in the inverse formula and simplify, and see what happens.


You can also try to substitute (4-x)/5 for x IN THE ORIGINAL FORMULA for f(x), simplify and see what happens.



You can do the graphs of the lines.
Put these on the same coordinate system:  {{{system(y=-5x+4,and,y=4/5-x/5)}}}