i know its a complicated way of showin....but im new so not dat much experienced....
u found perfect square in (i)...
use dat 1 2 find de g-1
(i) =2(X-2)2+1....
let g(x)= y
y=2(x-2)2 +1...
(y-1)/2= (x-2)2...
{(y-1)/2}1/2= (x-2)...
[{(y-1)/2}1/2]+2=x...
hence g-1(x)=[{(x-1)/2}1/2]+2...
NOW PUT K VALUE....K=2...
g-1(2)=9/4