If f(x)=2/(x+1), then what is the value of f^-1(1/5)?
We can solve this as follows
1/5 =2 / (x + 1)
x + 1 = 2 / (1/5)
x + 1 = 10
x = 9
So
f-1( 1/5) = 9
Proof
f(9) =1/5 so (9,1/5) is on the graph of f
f-1 reverses the coordinates so (1/5, 9) is on the graph of the inverse
$f^{-1}(1/5) = \frac{4}{3}$
