The value of parameter , for which the function f(x)=1+x α , α ≠ 0 is the inverse of itself is
-2
-1
1
2
let fx=1+xα =y⇒ x =y-1α ⇒f-1x=x-1α since f-1x=fx ⇒x−1α=1+α x
⇒α=−1