Answer
$d=-7$
Work Step by Step
The given equation is
$\Rightarrow d^2+14d+49=0$
Rewrite $14d$ as $7d+7d$.
$\Rightarrow d^2+7d+7d+49=0$
Group the terms.
$\Rightarrow (d^2+7d)+(7d+49)=0$
Factor each group.
$\Rightarrow d(d+7)+7(d+7)=0$
Factor out $(d+7)$.
$\Rightarrow (d+7)(d+7)=0$
Use zero product property.
$\Rightarrow d+7=0$ or $d+7=0$
Solve for $d$.
$\Rightarrow d=-7$ or $d=-7$
The solution is $d=-7$.
