\(a,=x^2-2x-x+2\\ =x\left(x-2\right)-\left(x-2\right)\\ =\left(x-1\right)\left(x-2\right)\\ b,=2x^2-2x+x-1\\ =2x\left(x-1\right)+\left(x-1\right)\\ =\left(2x+1\right)\left(x-1\right)\\ c,=x^2-2x+3x-6\\ =x\left(x-2\right)+3\left(x-2\right)\\ =\left(x+3\right)\left(x-2\right)\\ d,=3x^2-6x-x+2\\ =3x\left(x-2\right)-\left(x-2\right)\\ =\left(3x-1\right)\left(x-2\right)\)