Bài 1:
\(c,=6x^3-15x^2+3x\\ d,=4x^2+8x+x^2+2x-15=5x^2+10x-15\)
Bài 2:
\(c,=6x\left(x^2-2x-3\right)=6x\left(x^2-3x+x-3\right)=6x\left(x-3\right)\left(x+1\right)\\ d,=x\left(x+5\right)+y\left(x+5\right)=\left(x+y\right)\left(x+5\right)\)
Bài 3:
\(c,\Leftrightarrow\left(x+3\right)\left(x+2\right)=0\Leftrightarrow\left[{}\begin{matrix}x=-3\\x=-2\end{matrix}\right.\\ d,\Leftrightarrow x^2-6x+9-x^2+9x=9\\ \Leftrightarrow3x=-9\Leftrightarrow x=-3\)