Hello from MrBillDoesMath!
Answer:
y = 5(1.5)^x
Discussion:
y = ab^x
When x =1 , y = 7.5
7.5 = ab (*)
When x = 3, y = 16.875
16.875 = ab^3 (**)
Divide (**) by (*)
16.875/7.5 = ab^3/(ab) => 16.875/7.5 = 2.25
2.25 = b^2 => take square root of both sides
b = 1.5
So far, y = a (1.5)^x.
Substituting x = 1, y =7.5 in the equation gives
7.5 = a (1.5)^1 => as (1/5)^1 = 1.5
7.5 = a * 1.5 => divide both sides by 1,5
a = 7.5/1.5 =>
a = 5
The equation is y = 5(1.5)^x
Thank you,
MrB
