dx/dt = 3/2 units/s

dy/dt = 2x*dx/dt = 3x units/s

The overall rate of change will be:

ds/dt = sqrt{(dx/dt)^2 + (dy/dt)^2} units/s

(Think of this as a speed with x and y components.)

Thus

ds/dt = sqrt{9/4 + 9x^2} units/s

Thus

ds/dt(1, 2) = sqrt{9/4 + 9*1^2} units/s = sqrt{45/4} units/s = (3/2)*sqrt{5} units/s

-Dan