Find the formula for an exponential function

Question

Find the formula for an exponential function that passes through the two points given. and 

Answer 1

y = a·b^x

Plug in (0,7):

7 = a·b⁰

7 = a·1

7 = a

y = 7·b^x

Plug in (4,16807)

16807 = 7·b⁴

2401 = b⁴

7 = b

y = 7·7^x = 7^x+1