计算1.(x+y)(x-y)+(y-z)(y+z)+(z-x)(z+x) 2.(a+b-3)(a+b+3)

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计算1.(x+y)(x-y)+(y-z)(y+z)+(z-x)(z+x) 2.(a+b-3)(a+b+3)

计算1.(x+y)(x-y)+(y-z)(y+z)+(z-x)(z+x) 2.(a+b-3)(a+b+3)
计算1.(x+y)(x-y)+(y-z)(y+z)+(z-x)(z+x) 2.(a+b-3)(a+b+3)

计算1.(x+y)(x-y)+(y-z)(y+z)+(z-x)(z+x) 2.(a+b-3)(a+b+3)
1.(x+y)(x-y)+(y-z)(y+z)+(z-x)(z+x)
=x²-y²+y²-z²+z²-x²
=0
2.(a+b-3)(a+b+3)
=(a+b)²-9
=a²+2ab+b²-9

1=0
2=a^2+2ab+b^2-9