\(C=\sqrt{x^2+4x+4}+\sqrt{x^2+6x+9}\)
\(C=\sqrt{\left(x+2\right)^2}+\sqrt{\left(x+3\right)^2}\)
\(C=\left|x+2\right|+\left|x+3\right|\)
\(C=\left|x+2\right|+\left|-x-3\right|\ge\left|x+2-x-3\right|=1\)
Vậy : \(Min_C=1\Leftrightarrow-2\ge x\ge-3\)