Answer
$49$, $(p+7)^2$
Work Step by Step
To complete the square of $p^2 + 14p$, we add $(b/2)^2$. In this case, the "$b$" is the second coefficient, $14$. Thus, we add $(14/2)^2=49$ and so we have $p^2 + 14p+49$. Then by factorization, we get
$$
p^2 + 14p+49=(p+7)^2
.$$
