Answer:
The base (b) has to be positive and different of 1. The logarithm is the inverse of exponential, so:
logb(a) = x ⇒ a = bˣ
So, for b = 0 ⇒ 0ˣ = a
And there is impossible, "a" only could be 0.
For b = 1 ⇒ 1ˣ = a
And the same thing would happen, the logarithming would be to be 1, and the function will be extremally restricted.
For b<0, then the expression a = bˣ will be also restricted, and will not represent all values of a.
So, 0<b<1 and b >1.
