(a) Derive an equation for S, where N(x,t) = f(x - ct) is a solution to the diffusion equation with exponential growth, dN/dt = DdN/dt +9N. (b) Find the minimum wave speed, below which the solutions become complex. For this value of c, find the solutions fle) that are always > 0. (c) Sketch your solution for t = 0, t= 1, 1 = 2.
