數學連算計算問題

2013-10-21 9:20 pm
21x21x21-21x21-20=
(請問有簡易算法嗎?)

回答 (2)

2013-10-21 9:48 pm
✔ 最佳答案
21*21*21-21*21-20=21*21*(21-1)-20=441*20-20=440*20=8800
2013-10-21 9:35 pm
21x21x21-21x21-20
= 21x21x(21-1) –20
= 21*21*20 –20
= 20(21*21-1)
= 20*(21+1)(21-1)
( 利用 a^2 -b^2 = (a+b)(a-b) )
= 20*22*20
= 400*22
= 8800


收錄日期: 2021-04-30 18:05:29
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20131021000016KK01673

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