\(a,\Leftrightarrow x\left(x+3\right)-\left(x-3\right)\left(x+3\right)=0\\ \Leftrightarrow\left(x-x+3\right)\left(x+3\right)=0\\ \Leftrightarrow x=-3\\ b,A:B=\left(2x^2-x+4x-2\right):\left(2x-1\right)\\ =\left(2x-1\right)\left(x+2\right):\left(2x-1\right)\\ =x+2\)


