分类：教育/科学-学习帮助
问题：初二数学题1.(x^2+xy+y^2)^2
1.(x^2+xy+y^2)^2-4xy(x^2+y^2)

2.5(2a-1)(a-2)-3(2-a)^2

3.已知x+y-2=0,求(x^2-y^2)^2-8(x^2+y^2)的值

回答：1.(x^2+xy+y^2)^2-4xy(x^2+y^2)
=［(x+y)^2-xy］^2-4xy［(x+y)^2-2xy］
=(x+y)^4-6xy(x+y)^2+9x^2y^2
=［(x+y)^2-3xy］^2
=(x^2-xy+y^2)^2

2.5(2a-1)(a-2)-3(2-a)^2=(a-2)(10a-5-3a+6)=(a-2)(7a+1)

3.已知x+y-2=0,求(x^2-y^2)^2-8(x^2+y^2)的值

x+y=2,(x^2-y^2)^2-8(x^2+y^2)=［(x+y)(x-y)］^2-8(x^2+y^2)
=4(x-y)^2-8(x^2+y^2)=-4x^2-8xy-4y^2=-4(x+y)^2=-16