Y intercept of a function can be obtained by evaluating the value of the function when x=0, i.e.
y-intercept of f(x) = f(0)
Here, f(x) = 4^(x)
so y-intercept = f(0) = 4^0 = 1
All exponential functions have the y-intercept (0,1):
e^(0) = 1
10^0= 1
and so on.
