x cos(y) + y cos(x) − 1 = 0 dy dx sin(xy) + 3y = 4 ( π 2 , 1) sin(xy) + e xy = e x (π, 1) x 3 + y 3 = 3xy ( 3 2 , 3 2 ) 2xy − π sin(y) = 2π (1, π 2 ) 2y 3 + y 2 − y 5 = x 4 − 2x 3 + x 2 x m X v x 1 2 m(v 2 − v 2 0 ) = 1 2 k(x 2 0 − x 2 ) k, v 0 x 0 v = 0 m dv dt = − kx. d 2 x dt 2 = dv dt = a dx dt = v