Answer
741 Joules
Work Step by Step
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:
$U = 741 \ J$
