1) x^2 +x^2+x-1=x^2 +x+x^2-1=x(x+1) +(x+1)(x-1)=(x+1)(x+x-1)=(x+1)(2x-1)
2) 3x^2 +x-2=3x^2+3x-2x-2=3x(x+1)-2(x+1) =(x+1)(3x-2)
3) 2x^2+x-3=3x^2-x^2+x-3=3x^2-3-x^2+x=3(x^2-1)-x^2+x=
3(x+1)(x-1)-x(x-1) =(x-1)(3x+3-x)=(x-1)(2x+3)
4)2x^2+3x+1=3x^2-x^2+3x+1=3x^2+3x-x^2+1=3x(x+1)-(x^2-1)=
3x(x+1)-(x+1)(x-1)=(x+1)(3x-x+1)=(x+1)(2x+1)
5) 2x^2-x-3=3x^2=x^2-x-3=3x^2-3-x^2-x=3(x^2-1)-(x^2+x)
3(x+1)(x-1)-x(x+1)=(x+1)(3x-3-x)=(x+1)(2x-3)
6)3x^2-x-2=2x^2+x^2-x-2=2x^2-2-x^2-x=2(x^2-1)-x(x-1)=
2(x+1)(x-1)-x(x-1)=(x-1)(2x+2-x)=(x-1)(x+2)