Inverse Functions:
The inverse of a function f(x) is another function, f^-1(x), which reverses f(x).
First you should write out the equation x=f(y) (which is the same as f(x), just with y’s instead of x’s.
Then you should rearrange the equation to make y the subject.
Finally, replace y with f^-1(x).
Example 1:
If f(x) = 12 + x / 3, find f^-1(x)
x = 12 + y / 3
3x = 12 + y
y = 3x - 12
f^-1(x) = 3x - 12
Example 2:
If f(x) = 3 / 2x+5, show that ff^-1(x) = x
Inverse function - f^-1 = 3/2x - 5/2
Substitute f^-1(x) into f(x)
ff^-1(x) = 3/2(3/2x - 5/2)+5
= 3/(3/x - 5 +5)
= 3/(3/x)
= 3 x x/3
= x
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