Precalculus (6th Edition) Blitzer

Solution set = $\{-6,-1\}$
Use the square root property: If $u^{2}=d$ then $u=\pm\sqrt{d}$ Here, $u=2x+7, \quad d=25,\quad\sqrt{d}=5$ Apply the property $2x+7=\pm 5 \quad$ ... add $-7$ to both sides $2x=-7\pm 5\quad$ ... divide with $2$ $x=\displaystyle \frac{-7\pm 5}{2}\Rightarrow\left\{\begin{array}{l} x=\frac{-7-5}{2}=-6,\\ \\ x=\frac{-7+5}{2}=-1 \end{array}\right.$ Solution set = $\{-6,-1\}$