\(\Leftrightarrow x^2+4x+4-x^2+9=-3\Leftrightarrow4x=-16\Leftrightarrow x=-4\)
\(\left(x+2\right)^2-\left(x-3\right).\left(x+3\right)=-3\)
\(x^2+4x+4-\left(x-3\right)\left(x+3\right)=-3\)
\(x^2+4x+4-x^2+9=-3\)
\(4x+4+9=-3\)
\(4x+13=-3\)
\(4x=-3-13\)
\(4x=-16\)
\(x=-16:4\)
\(x=-4\)