## Essential University Physics: Volume 1 (4th Edition)

We know that the potential energy is equal to the negative integral of force as a function of distance. Thus, we find: $U = - \int_{x_1}^{x_2}F(x)dx$ $U = - \int_{0}^{x}(-kx - bx^2)dx$ $U = -\frac{1}{2}kx^2 - \frac{1}{3}bx^3$ Plugging in the given values, we find: $U = 741 \ J$