Answer
$$d=2,\:d=-1$$
Work Step by Step
Completing the square to solve the equation, we find:
$$d^2-d-2+\left(-\frac{1}{2}\right)^2-\left(-\frac{1}{2}\right)^2 \\ \left(d-\frac{1}{2}\right)^2-2-\left(-\frac{1}{2}\right)^2 \\ \left(d-\frac{1}{2}\right)^2-\frac{9}{4} \\ \left(d-\frac{1}{2}\right)^2=\frac{9}{4} \\ d=2,\:d=-1$$
