physics
posted by Hope .
A 1.6 kg particle moving along the xaxis experiences the force shown in the figure. The particle's velocity is 4.2 m/s at x = 0 m.
The figure or graph has F (N) along the y axis and velocity along the x axis. A diagonal line drops from positive 10 force to 10 force from 0 cm to 4 cm. and crosses the x axis at 2 cm.
What is its velocity at 2 cm and 4 cm?
What formula do I need to use?

Integrate F dx from 0 to 0.02 m to get the change in kinetic energy (KE) at 2 cm. Use the new value of the KE to get the new velocity. Then do it again for 0.02 to 0.04 m. The KE will decrease, since the force on the particle is in the opposite direction to motion over that interval.

Please explain to me how to integrateI am unsure exactly what this means in this problem
Thanks 
Find the area under the line within each interval