b1
P+Q =3ab+a^2-2b^2+2a^2-3ab
=3a^2-2b^2
P-Q=3ab+a^2-2b^2-2a^2+3ab
=6ab-a^2-2b^2
Q-P=2ab^2-3ab-3ab-a^2+2b^2
=a^2+2b^2-6ab
b2
A+B=3x^2+2xy-4y^2+4y^2-2xy+3x^2y^2-x^2
=2x^2+3x^2y^2
A-B=3x^2+2xy-4y^2-4y^2+2xy-3x^2y^2+x^2
=4x^2+4xy-8y^2-3x^2y^2
B3:
M=(5x^2+3y-xy)-(x^2 +xy+y^2)
=5x^2+3y^2-xy-x^2-xy-y^2
=4x^2+2y^2-2xy