展开全部
①:104²(巧算)
解:原式=100²+2×100×4+4²
=10000+800+16
=1086
②:198²=(200-2)²
解:原式=200²-2×200×2+2²
=40000-800+4
=39204
③: (xy+z)(-xy+z)
解:原式=-(xy+z)(xy+z)
=-(xy+z)²
=-(xy²+2xyz+z²)
=-x²y²-2xyz-z²
④:(-x-y)(x+y)
解:原式=-(x+y)(x+y)
=-(x+y)²
=-x-2xy-y²
⑤:(x-2)(x+2)(x²+4)
解:原式=(x²-4)(x²+4)
=x的四次方-16
解:原式=100²+2×100×4+4²
=10000+800+16
=1086
②:198²=(200-2)²
解:原式=200²-2×200×2+2²
=40000-800+4
=39204
③: (xy+z)(-xy+z)
解:原式=-(xy+z)(xy+z)
=-(xy+z)²
=-(xy²+2xyz+z²)
=-x²y²-2xyz-z²
④:(-x-y)(x+y)
解:原式=-(x+y)(x+y)
=-(x+y)²
=-x-2xy-y²
⑤:(x-2)(x+2)(x²+4)
解:原式=(x²-4)(x²+4)
=x的四次方-16
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