+130516
This function has no inverse because it is not one- to-one
However......if we restrict the domain of the original function, we can get two separate inverses
y = 9x^2 divide both sides by 9
y/9 = x^2 take the pos/neg square roots of both sides
[pos/neg] sqrt( y/9) = x exchange x and y
[pos/neg] sqrt( x/9) = y = f-1(x)
If the domain of the original function is from (-inf, 0), then neg sqrt(x/9) is the inverse
If the domain of the original function is from (0, inf), then pos sqrt(x /9) is the inverse
[ BTW, the origin point (0, 0) could belong to either inverse function ]
