[tex]\bf (x+5)(x+6)=0\implies
\begin{cases}
x+5=0\implies &x=-5\\
x+6=0\implies &x=-6
\end{cases}
\\\\\\
(x-9)(x+8)=0\implies
\begin{cases}
x-9=0\implies &x=9\\
x+8=0\implies &x=-8
\end{cases}
\\\\\\
(x+4)(x-4)=0\implies
\begin{cases}
x+4=0\implies &x=-4\\
x-4=0\implies &x=4
\end{cases}
\\\\\\
x^2-14x+49\implies (x-7)^2\iff (x-7)(x-7)
\\\\\\
(x-7)(x-7)=0\implies
\begin{cases}
x-7=0\implies &x=7\\
x-7=0\implies &x=7
\end{cases}[/tex]
