1) 4a^2b-3ab^2-a^2b+2ab^2=3a^2b-3ab^2+2ab^2=3a^2b-ab^2=ab*(3a-b)
2) x^2+4x-5+x^2-3x+2=3x^2+x-3=2x^2+3x-2x-3=x(2x+3)-(2x+3)=(2x+3)*(x-1)
3)10a-6b+5c-4d+9a-2b-8c-2d=19a-8b-3c-6d
4)2a^4-8a^3t-2a^2b^2-4ab^3-3a^4+8a^3b+9a^2b^2+ab^3=-a^4-8a^3t+7a^2b^2-3ab^3+8a^3b=-a(a^3+8a^2t-7ab^2+3b^3-8a^2b)