Re: [計量] 想請問一題數學
※ 引述《miue (想要簡單的幸福)》之銘言：
: How many two-digit positive integers N have the
: property that the sum of N and the number obtained
: by reversing the order of the digits of N is a perfect
: square?
: (A) 4
: (B) 5
: (C) 6
: (D) 7
: (E) 8
: Answer: (E)
: 麻煩大家嚕!
: thanks~
設此兩位數的長相為" xy "，則此數的值是" 10x + y "
則reversing the order of the digits of N後，長相為" yx "，值為" 10y + x "
sum = (10x+y) +(10y+x) = 11(x+y) = 完全平方數，
=> x+y = 11
=> (x,y) = (9,2),(8,3),(7,4),(6,5),
(2,9),(3,8),(4,7),(5,6). 共8組。
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07/16 17:10, , 1F
07/16 17:10, 1F
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