How do you find the inverse of f(x) = 4/xf(x)=4x?

1 Answer
May 12, 2018

The inverse is x = 4/(f(x))x=4f(x) or f(x) = 4/xf(x)=4x
(same as original)

Explanation:

To find the inverse, we swap the x and y values.

The original equation is f(x) = 4/xf(x)=4x, meaning that the inverse would be x = 4/(f(x))x=4f(x).

If you want it with f(x)f(x) by itself, first multiply f(x)f(x) on both sides of the equation:
x quadcolor(blue)(*quadf(x)) = 4/f(x) quadcolor(blue)(*quad(f(x))

x(f(x)) = 4

Divide both sides by color(blue)x:
(x(f(x)))/color(blue)x = 4/color(blue)x

Therefore,
f(x) = 4/x

As you can see, the inverse is the same as the original equation. This can be proved by graphing both equations:
Graphing original f(x) = 4/x:
enter image source here

Graphing inverse x = 4/f(x):
enter image source here
(desmos.com)

As you can see, both graphs are the same.

Hope this helps!