Question 121270
{{{f(x)=5x + 4}}} Start with the given function



{{{x=5f(x) + 4}}} Interchange x and f(x)



Now solve for f(x)



{{{x-4=5f(x)}}} Subtract 4 from both sides



{{{(x-4)/5=f(x)}}} Divide both sides by 5



{{{f(x)=(1/5)x-4/5}}} Break up the fraction




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Answer:

So the inverse function is 



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