If for some \( p, q, r \in \mathbb{R} \), not all have same sign, one of the roots of the equation \( (p^{2}+q^{2})x^{2}-2q(p+r)x+q^{2}+r^{2}=0 \) is also a root of the equation \( x^{2}+2x-8=0 \), then \( \dfrac{q^{2}+r^{2}}{p^{2}} \) is equal to __________.
