Help me out please???

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

Lucy is a dress maker. she sews \dfrac47 7 4 of a dress in \dfrac34 4 3 hour. lucy sews at a constant rate. at this rate, how many dresses does lucy sew in one hour? include fractions of dresses if applicable

In which direction does the left side of the graph of this function point? f(x) = 3x3 - x2 + 4x - 2