Answer
The work done on the particle as it move from x = 0 to x = d is $\frac{qd^3}{3}$
Work Step by Step
$W = \int_{0}^{d}~F_x~dx$
$W = \int_{0}^{d}~qx^2~dx$
$W = \frac{qx^3}{3}~\Big\vert_{0}^{d}$
$W = \frac{qd^3}{3}$
Therefore, the work done on the particle as it move from x = 0 to x = d is $\frac{qd^3}{3}$.
