3. Let $p$ be a real number such that the equation $2 y^{2}-8 y=p$ has only one solution. Then
(A) $p-8$
(D) $p=-8$
(E) $p<-8$
3. Ans: D
Since the equation $2 y^{2}-8 y-p=0$ has only one solution, its discriminant
$$
(-8)^{2}-4 \times 2 \times(-p)=0 .
$$

Thus $p=-8$.