The only force acting on a 1.8 kg body as it moves along the positive x axis has an x component Fx = - 6x N, where x is in meters. The velocity of the body at x = 3.0 m is 8.0 m/s. (a) What is the velocity of the body at x = 4.0 m? (b) At what positive value of x will the body have a velocity of 5.0 m/s? I think to start off i need to take the integral of Fx=-6xN, which would be -3x^2. But from there i'm a bit confused. It doesn't give the force acting on it, so i don't know how to find the work since W=F*Fx.