f(3)=-3/8 and (f-2)=-12

MY SOLUTION
F(-2)=ab^-2 = -12
F( 3)=ab^ 3 = -3/8

b^5 = 12 * 3/8 = 32

b=2

12 = a(2)^2

12 = 4a

a =3

f(x)=3(2)^x

no.

check it
f(3)=ab^3=3*2^3=24, not -3/8

recheck your work.