1.(x^2+xy+y^2)^2-4xy(x^2+y^2)2.5(2a-1)(a-2)-3(2-a)^23.已知x+y-2=0,求(x^2-y^2)^2-8(x^2+y^2)的值4.a^3-5a+45.(x-y)^2+3(x^2-y^2)-4(x+y)^26.2m^2(n+2)-12mn-3n^2
热心网友
1.(x^2+xy+y^2)^2-4xy(x^2+y^2) =（x^2+y^2)^2+2xy(x^2+y^2)+x^2y^2-4xy(x^2+y^2) =（x^2+y^2)^2-2xy(x^2+y^2)+x^2y^2 =（x^2-xy+y^2)^2
热心网友
(x^2+xy+y^2)^2-4xy(x^2+y^2)=[(x^2+y^2)+xy]^2-4xy(x^2+y^2)=(x^2+y^2)^2+2xy(x^2+y^2)+(xy)^2-4xy(x^2+y^2)=(x^2+y^2)^2-2xy(x^2+y^2)+(xy)^2=(x^2-xy+y^2)^2－－－－－－－－－－－－－－－5(2a-1)(a-2)-3(2-a)^2=(a-2)[5(2a-1)-3(a-2)]=(a-2)(10a-5-3a+6)=(a-2)(7a+1)－－－－－－－－－－－－－－－已知x+y-2=0,求(x^2-y^2)^2-8(x^2+y^2)的值(x^2-y^2)^2-8(x^2+y^2)=[(x-y)(x+y)]^2-8(x^2+y^2)=[(x-y)^2][(x+y)]^2-8(x^2+y^2)=4(x-y)^2-8(x^2+y^2)=-4(x+y)^2=-4*2*2=-16－－－－－－－－－－－－－－－－－a^3-5a+4=(a^3-a)-(4a-4)=a(a^2-1)-4(a-1)=a(a-1)(a+1)-4(a-1)=(a-1)(a^2+a-4)－－－－－－－－－－－－－－－－－－(x-y)^2+3(x^2-y^2)-4(x+y)^2=(x-y)^2+3(x-y)(x+y)-4(x+y)^2=[(x-y)+4(x+y)][(x-y)-(x+y)]=-2y(5x+3y)－－－－－－－－－－－－－－－－－－2m^2(n+2)-12mn-3n^2 =2m^2*n+4m^2-12mn-3n^2 =?。