(1)x=3t^2-4tdx/dt = 6t-4y=-t^3+3tdy/dt = -3t^2+3质点的初速度 = ( dx/dt , dy/dt) = ( 6t-4 , -3t^2+3)(2)dx/dt = 6t-4d^2x/dt^2 =6dy/dt = -3t^2+3d^2y/dt^2 = -6td^2y/dt^2 |t=1 = -6t=1s时质点的加速度 = ( 6, -6)