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计算,
(x-3y)(x+3y)-(x-3y)^2
112^2-113×111
(2x-3)(x+4)
人气:434 ℃ 时间:2020-03-25 01:19:43
解答
(x-3y)(x+3y)-(x-3y)^2
=x²-9y²-(x²-6xy+9y²)
=-18y²+6xy
112^2-113×111
=112²-(112+1)(112-1)
=112²-(112²-1²)
=1
(2x-3)(x+4)
=2x²+8x-3x-12
=2x²+5x-12
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