f ( f(x) ) =
1 1 5x - 2 5x - 2
_________________ = _____________ = ___________ = ________
5 (1 / (5x - 2)) - 2 5 / (5x - 2) - 2 5 - 2 (5x - 2) 9 - 10x
The x not in the domain of this function is the one that makes 9 -10x = 0
So....
9 -10x = 0
9 = 10x
x = 9 /10
