Which exponential function goes through the points (1, 8) and (4, 64)?

An exponential function can be expressed as:

y=ab^x  we have two points so we can solve

64/8=(ab^4)/(ab^1)

8=b^3

2=b, now we have:

y=a(2^x), using point (4,64)

64=a(2^4)

64=16a

4=a so

y=4(2^x)

21, i'm pretty sure it's right lol