1.x^2-y^2=(x^2+xy)-(xy+y^2) =3-(-2) =52. x^2+4xy+3y^2=(x^2+xy)+3(xy+y^2) =3+3*(-2) =-3
x^2-y^2=（x^2+xy）—(xy+y^2)=3+2=5x^2+4xy+3y^2=（x^2+xy）+3（xy+y^2)=3-6=-3
