If the function `f:[1,oo)->[1,oo)` is defined by `f(x)=2^(x(x-1)),` then `f^-1(x)` is (A) `(1/2)^(x(x-1))` (B) `1/2 sqrt(1+4log_2x)` (C) `1/2(1-sqrt(1+4log_2x))` (D) not defined

Explanation

`f(x)=2^{(x+1)} text {, ie., } y=2^{x(x-1)}`
`


=log _{2} y=x(x-1)=x^{2}-x`
`


=x^{2}-x-log _{2} y=0`
`

...