Solve -pdp=qdq

$$- p d p = q d q$$

Solve for d

$$\left\{\begin{matrix}\\d=0\text{, }&\text{unconditionally}\\d\in \mathrm{R}\text{, }&p=0\text{ and }q=0\end{matrix}\right.$$

Steps for Solving Linear Equation

Multiply q and q to get q^{2}.

$$\left(-p\right)dp=q^{2}d$$

Subtract q^{2}d from both sides.

$$\left(-p\right)dp-q^{2}d=0$$

Multiply p and p to get p^{2}.

$$-p^{2}d-q^{2}d=0$$

Combine all terms containing d.

$$\left(-p^{2}-q^{2}\right)d=0$$

Divide 0 by -p^{2}-q^{2}.

$$d=0$$

Solve for p

$$\left\{\begin{matrix}p=0\text{, }&q=0\\p\in \mathrm{R}\text{, }&d=0\end{matrix}\right.$$