The function f(x)=x2f(x) = x^2f(x)=x2 is restricted to the domain x≤0x \le 0x≤0. What is the inverse function f−1(x)f^{-1}(x)f−1(x)?
f−1(x)=xf^{-1}(x) = \sqrt{x}f−1(x)=x
f−1(x)=−xf^{-1}(x) = -\sqrt{x}f−1(x)=−x
f−1(x)=−xf^{-1}(x) = \sqrt{-x}f−1(x)=−x
f−1(x)=−−xf^{-1}(x) = -\sqrt{-x}f−1(x)=−−x