Question

数学题 回答好的追分

合并同类项

（1）2（x+y)＾2+8(y-x)＾2 提示：把（x-y）看成一个整体

Answer 1

解：原式=2[(x+y)^2-4(x-y)^2]
=2(x+y+2x-2y)(x+y-2x+2y)
=2(3x-y)(-x+3y)
=2(-3x^2+10xy-3y^2)
=-6x^2+20xy-6y^2

Answer 2

2（x+y)＾2+8(y-x)＾2
=2[(x-y)^2+4xy]+8(y-x)＾2
=10(x-y)^2+8xy

Answer 3

解：原式=2[(x+y)^2-4(x-y)^2]
=2(x+y+2x-2y)(x+y-2x+2y)
=2(3x-y)(-x+3y)
=2(-3x^2+10xy-3y^2)
=-6x^2+20xy-6y^2
=-2(3x^2-10xy+3y^2)