How do you find the inverse of $f (x) = \frac{x}{5} + 4$ $f(x)=x/5+4$ ?

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How do you find the inverse of $f (x) = \frac{x}{5} + 4$ $f(x)=x/5+4$ ?

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Answer 1 · 2015-11-14T16:59:26

Say that $f (x) = y$ $f(x) = y$ , then isolate $x$ $x$ .

$y = \frac{x}{5} + 4$ $y = x/5 + 4$
$y - 4 = \frac{x}{5}$ $y - 4 = x/5$
$5 y - 20 = x$ $5y - 20 = x$

Call $x$ $x$ $f^{- 1} (x)$ $f^(-1)(x)$ , or $f (y)$ $f(y)$ or just $x$ $x$ , whichever you prefer, I myself prefer $f (y)$ $f(y)$ . If you've chosen $f (- 1) (x)$ $f(-1)(x)$ then you need to change $y$ $y$ to $x$ $x$ .

$f (y) = 5 y - 20$ $f(y) = 5y - 20$
$f^{- 1} (x) = 5 x - 20$ $f^(-1)(x) = 5x - 20$
$x = 5 y - 20$ $x = 5y - 20$

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How do you find the inverse of $f (x) = \frac{x}{5} + 4$ $f(x)=x/5+4$ ?

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