f(x) = 2−xx, x ≠ 0
let the inverse of f 2−1x, be y
y = 2−xx,
xy = 2 - x
xy + x = 2
x(y + 1) = 2
x = 2y+1 ⇒ 2x+1
Thus, the inverse of f(x) = 2−xx, x ≠ 0 = 2x+1 provided x ≠ -1