1.(x+y)²-(x-y)²
2.每個蘋果值$m,每個橙值$n,現彼得買蘋果3個,橙4個,付$20,應找回多少?
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2007-08-22 10:44 pm
回答 (2)
2007-08-22 11:27 pm
✔ 最佳答案
1. (x+y)²-(x-y)² = [(x+y)(x+y)]-[(x-y)(x-y)]
= (x²+2xy+y²) - (x²-2xy+y²)
= x²+2xy+y²-x²+2xy-y²
= x²-x²+2xy+2xy+y²-y²
= 4xy
2. 蘋果3個: $3m; 橙4個: $4n
應找回: $(20-3m-4n)
2007-08-22 10:48 pm
1. (x+y)²-(x-y)² = x² + 2xy +y² - x² + 2xy - y² = 4xy
2. 20 - 3m -4n
2. 20 - 3m -4n
參考: Me
收錄日期: 2021-04-13 18:54:26
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https://hk.answers.yahoo.com/question/index?qid=20070822000051KK02862