## anonymous 5 years ago if f(x)=x^2 -1. what is the equation for f^-1(x) ....f^-1(x)= +/- (squareroot all)x+1 ...f^-1(x)= +/- (squareroot all )x-1 ....f^-1(x)= +/- (squareroot x only) x+1 ....f^-1(x)= +/- (squareroot x only) x-1

1. anonymous

$y=x^2-1$ switch x and y $x=y^2-1$ solve for y $x+1=y^2$ $y=\pm\sqrt{x+1}$

2. anonymous

but this is not a function, so cannot be one of the answers. did they restrict the domain of f?

3. anonymous

nope

4. anonymous

then there is a mistake here some place. you cannot write $f^{-1}(x)=\pm\sqrt{x+1}$ because a function cannot have two answers. on the other hand you are not allowed just to pick one