Question

If f(x) = 5x + 4, which of the following is the inverse of f(x)?
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Answer 1

set f(x) equal to y

y = 5x + 4

swap x and y

x = 5y + 4

make y the subject

x - 4 = 5y

$y = \frac{x - 4}{5}$

replace y with f^-1(x)

$f(x) = \frac{x - 4}{5}$