5 = a b^3 10 = a b^4
solving the first one, you get a = 5/(b^3)
substituting that into the second equation
10 = 5/(b^3) b^4
10 = 5b
b=2
5=a 2^3
5=8a
a=5/8
y= (5/8) 2^x
check with the second point
10=(5/8) 2^4
10=(5/8) 16
10=10
y= (5/8) 2^x is the exponential model.