What is the a-value in the base exponential function stand for?​

Ac contractor is building a new subdivision outside of the city. he has started work on the first street and is planning on the other streets to run in a direction parallel to the first. the second street will pass through (-2,4) find the equation of the location of the second street in standard form. a.2x+y=2 b. x-y=2 c.2x+y=2 d. x+y=2

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

Me. i can't figure out this question. give an explanation too. .