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初一简便计算 (1)51*49 (2)99²
人气:106 ℃ 时间:2020-01-19 07:04:40
解答
51*49
=(50+1)(50-1)
=50²-1²
=2500-1
=2499
99²
=(100-1)²
=100²-2x1x100+1²
=10000-200+1
=9800+1
=9801
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