Question:
Show that $x=-3$ is a solution of $x^{2}+6 x+9=0$.
Solution:
Given that the equation $x^{2}+6 x+9=0$
$x^{2}+3 x+3 x+9=0$
$x(x+3)+3(x+3)=0$
$(x+3)(x+3)=0$
$(x+3)^{2}=0$
Square root both side, we get
$(x+3)=0$
$x=-3$
Therefore, $x=-3$ is the solution of given equation.
Hence, proved.