a wave moving along the x axis is described by y(x,t) = Ae^(-(x+vt)^2/b) where x is in meters and t is in seconds. Given A=4m, v=3 m/s, and b=4 m^2. Determine the speed of the wave. Answer in units of m/s. i tried using partial differentiation with respect to t. i got dy/dt = 4e^(-(3(x+3t))/2). I don't know what to do next. Please help.