Given the function f (x) = x-1-alnx, it is proved that f (x) ≥ 0 is constant if and only if a = 1

Given the function f (x) = x-1-alnx, it is proved that f (x) ≥ 0 is constant if and only if a = 1

If f (x) is derived, f '(x) = 1-A / X can be obtained. When x = a, the minimum value can be obtained. So the minimum value of F (a) is a-1-alna. If the minimum value ≥ 0 is constant, then f (x) ≥ 0 is constant. If f (a) is derived from a, then f' (a) = - LNA can be obtained