p=+8.

Step-by-step explanation:

In ax

2

+bx+c=0,

Discriminant D =b

2

−4ac,

D=0, for the roots to be real and equal

In 2x

2

+px+8=0

Thus, we have a=2,b=p and c=8

Then D =b

2

−4ac=0

∴p

2

−4×2×8=0⇒p

2

−64=0

⇒p=±8.