El cuarto término de la sucesión geométrica es125, y el décimo término es 125/64. Encuentre el término número 14

Given the equation f(x)=a(b)x where the initial value is 40 and the growth rate is 20% what is f(4)

Ineed in figuring out this problem.

Which statement is true about a number and its additive inverse? a. their product is always one. b. their sum is always one. c. they are always reciprocals of each other. d. their sum is always zero.