Answer
{$-\frac{2}{3}$}
Work Step by Step
Using the rules for factoring trinomials and setting the factors equal to zero, we obtain:
$9x^{2}+12x+4=0$
$9x^{2}+6x+6x+4=0$
$3x(3x+2)+2(3x+2)=0$
$(3x+2)(3x+2)=0$
$(3x+2)=0$ or $(3x+2)=0$
$x=-\frac{2}{3}$
Therefore, the solution set is {$-\frac{2}{3}$}.
