1.A boy finds $105 in $10,$5 and $1 coins.If there are 17coins in all,how many coins of each type-can he have?
2.Find a,b and c such that
x^2 - x + 3/(x^2 + 2)(2x - 1) = ax + b/x^2 + 2 + c/2x - 1
[Hint:Multiply through by (x^2 + 2)(2x - 1) and equate coeffiicients of powers of x.
maths questions
2007-11-01 1:25 am
回答 (1)
2007-11-02 3:23 pm
✔ 最佳答案
1)Let a be the number of $10 coins, b be the number of $5 coins, c be the number of $1 coins
10 * a + 5 * b + 1 * c = 105
10a + 5b + c = 105 --- (1)
a + b + c = 17 --- (2)
From (1) we know that c = 0 or 5
<the unit digit of 105 is 5, to attain 5, c must be 0 or 5, and c will not be 10, same reason>
For c = 0
10a + 5b = 105
a + b = 17
5a = 20
a = 4
b = 13
c = 0
For c = 5
10a + 5b + 5 = 105
10a + 5b = 100
a + b + 5 = 17
a + b = 12
5a = 40
a = 8
b = 4
c = 5
收錄日期: 2021-04-13 14:16:36
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20071031000051KK02246