Answer
Fill the blank with: the square root property.
Work Step by Step
The technique to use here is the square root property:
If $u^{2}=d$ then $u=\pm\sqrt{d}$
Here, $u=2x+7$, and what would follow is
$2x+7=\pm \sqrt{25}$
$2x=-7\pm 5$
$x=\displaystyle \frac{-7\pm 5}{2}$
Resulting in two solutions:
$x=\displaystyle \frac{-7-5}{2}=-6$, or
$x=\displaystyle \frac{-7+5}{2}=-1$
Fill the blank with: the square root property
