y = f(x) = a^x is an expo function with constant base a and exponent x. First, let's assume that a is positive and lying either in (0,1) or (1, infinity).
If a satisfies 0<a<1, then the expo fn is decreasing with x. Its y-intercept is (0,1) because a^0 = 1 for all a that satisfy (0,1). Same is true for (a>1).
In both cases the horiz. asymptote is the line y=0.
y = f(x) = a^x has only one intercept, the y-intercept, (0,1).
However, z = f(x) = a^x + C could have an x-intercept for certain C.
