Question

A square with side x cm, is changing with time where x(t) = 3t + 1. What is the rate of change of the area of the square when t = 2 seconds?

Answer 1

A = x^2 = (3t+1)^2 = 9 t^2 + 6 t + 1

dA/dt = 18 t + 6

when t = 2
dA/dt = 36 + 6 = 42