Question

(X-Y+Z) (Y-X-Z)

Answer 1

解：原式=(x-y+z)(-x+y-z)………………………………………………加法交换律
=(x-y+z)[-(x-y+z)]……………………………………………提取负号
=-(x-y+z)(x-y+z)……………………………………异号得负，绝对值相乘
(=-(x^2-xy+xz-xy+y^2-yz+xz-xy+x^2))可不写………………乘法分配律
=-(x^2+y^2+z^2-2xy-2yz+2xz)…………乘法分配律(在上上步骤的基础上)
=-x^2-y^2-z^2+2xy+2yz-2xz…………………………………去括号

Answer 2

(x-y+z)(y-x-z)
=-(x-y+z)(x-y+z)
=-(x-y+z)^2

=-(x^2+y^2+z^2-2xy-2yz+2xz)
=-x^2-y^2-z^2+2xy+2yz-2xz

Answer 3

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