**8/28/2014
****If
f(x) = x**^{2
}**+
2x – 4 for x **__>__**
****0,
what is the value of ***f***
**^{-1}**(4)?**

a) 2

b) 4

c) 5

d) 8

e) 10

**Scroll
down for the solution.**

**8/28/2014
**Solution.
**A.
**Since
we need *f
*^{-1}**(4),
if ***f
*^{-1}**(4)**
=
*x, ***f(x)
= 4 → x**^{2
}**+
2x – 4 = 4 so that x**^{2
}**+
2x – 8 = 0. Factoring and solving, x = 2.**