Given the function f (x) = loga (AX-1) (a > 0, a ≠ 1); (1) find the domain of definition of function f (x); (2) discuss the monotonicity of function f (x)

Given the function f (x) = loga (AX-1) (a > 0, a ≠ 1); (1) find the domain of definition of function f (x); (2) discuss the monotonicity of function f (x)

(1) From AX-1 > 0, we get ax > 1. (1 point) when a > 1, X > 0; (2 points) when 0 < a < 1, X < 0. (3 points) so the domain of definition of F (x) is x ∈ (0, + ∞) when a > 1; X ∈ (- ∞, 0) when 0 < a < 1. (4 points) (2) when a > 1, let x1, X2 ∈ (0, + ∞)