第1題
Find a two-digit number that satisfies the following conditions :
(1)The tens-digit is greater that the unit-digit by 2.
(2)The square of the unit-digit is karger that twice the tena-digit.
A possible solution is 64 .Would you suggest other solutions?
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ｔｈａｎｋ ｙｏｕ ～～
我有１題數學5識...help me (10點)
2007-07-24 7:04 pm
回答 (4)
2007-07-24 8:36 pm
✔ 最佳答案
Let x be the tens-digit , y be the unit-digit then , x-y=2------------(1)
and y ^2 > 2 x---------(2)
satisfies the above conditions
put (1) x=2+y into (2)
y^2>2(2+y)
=> y^2>4+2y
=> y^2-2y-4>0
=> y^2-2y+1-5 >0
=> (y-1)^2-5>0
so y >4(y<10), that mean
y=4, x=2+y=6
y=5, x=2+y=7
y=6, x=2+y=8
y=7, x=2+y=9
y=8, x=2+y=10(rejected)
y=9, x=2+y=11(rejected)
so the two-digit number will be 64, 75, 86, 97
參考: ME
2007-07-25 12:11 am
97 86 75 64
2007-07-24 8:31 pm
97
86
75
64
86
75
64
2007-07-24 7:14 pm
97
86
75
64
都係
86
75
64
都係
收錄日期: 2021-04-23 22:21:26
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070724000051KK01183