Given the function f (x) = (AX-2) / (x + 1) (1) it is proved that when a = 1, the function f (x) is an increasing function on (- 1, + ∞); (2) if the function f (x) is a Zeng function on (- 1, + ∞), the value range of a is obtained

Given the function f (x) = (AX-2) / (x + 1) (1) it is proved that when a = 1, the function f (x) is an increasing function on (- 1, + ∞); (2) if the function f (x) is a Zeng function on (- 1, + ∞), the value range of a is obtained

It is proved that: (1) let X1 be greater than - 1 and less than X2, then f (x2) - f (x1) = (x2-2) / (x2 + 1) - (x1-2) / (x1 + 1), which is reduced to [3 (x2-x1) + 2] / [(x1 + 1) (x2 + 1)], which is always greater than zero, so when a = 1, the function is an increasing function