Please help ASAP- this is Trig Any Angle practice

Two positive integers are 3 units apart on a number line. their product is 108. which equation can be used to solve for m, the greater integer? m(m – 3) = 108 m(m + 3) = 108 (m + 3)(m – 3) = 108 (m – 12)(m – 9) = 108

How to do this , and can some one explain

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