The function f (x) = loga (a-ka ^ x) and the domain of definition of function f (x) is a subset of set {X / X & lt; = 1}

The function f (x) = loga (a-ka ^ x) and the domain of definition of function f (x) is a subset of set {X / X & lt; = 1}

From the question, (a-ka ^ x) > 0
ka^x<a
k<1/(a^(x-1)
Because x ∈ (- ∞, 1]
x-1∈【0,+∞)
When a ∈ (0,1), 1 / (a ^ (x-1) ∈ [1, + ∞)
When a ∈ (1, + ∞), 1 / (a ^ (x-1) ∈ (0,1]
So to sum up
When a ∈ (0,1), K ∈ [1, + ∞)
When a ∈ (1, + ∞), K ∈ (0,1]