[開方{7+開方45)-開方(7-開方45)]點計
回答 (2)
2008-02-11 7:43 am
✔ 最佳答案
Let √(7 + √45) - √(7 - √45) = xSquaring both sides,
7 + √45 - 2√(7 + √45)(7 - √45) + 7 - √45 = x2
14 - 2√(49 - 45) = x2
x2 = 10
x = √10 (x must be positive)
2008-02-11 00:38:09 補充：
Hence, √(7 + √45) - √(7 - √45) = √10
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