Inverse Image function

Question

Let $A= [{5}, \infty[$ , $B=[{1}, \infty[$ and $f: A \to B, f(x)=x^2-{10}x+{26}$

Determine the inverse image $f^{-1}:\ B \to A, f^{-1}(x)$

How should I proceed with this?

Thanks in advance