I need help with this.

1. A particle of mass 2.5 kg moves under the influence of a force: F(x) = (-5x- +7x) N If its speed at x = 4.9 m is v = 14 m/s, what is its speed at x = -4.9 m? Speed at x = -4.9 m = Vm/s Think & Prepare: 1. Is this force constant over the displacement, or varies with displacement? How can you calculate the work done by this force? 2. How is the work done by all forces on an object related to its kinetic energy