A force $F = Ay^2 + By + C$ acts on a body in the y-direction. The work done by this force during a displacement from y = -a to y = a is
$ W = \int Fdy $ $ = \int _{-a} ^{+2} (Ay^2 +By +C)dy $ $ = \left[ { Ay^3 \over 3} + { By^2 \over 2} + cy \right] _{-a}^{+a} $ $ = { 2Aa^3 \over 3} + 2Ca $