關於二元一次的數學問題

daoloi

小弟有一題數學未能解答，請高人指點一下：

A shop has sold 129 records by Alan and Anita with a total sales of $12,615.
Each record by Alan and each record by Anita are sold at $110 and $95 respectively.
How many records

a) by Alan has the shop sold

...

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pollu002

A shop has sold 129 records by Alan and Anita with a total sales of $12,615.
Each record by Alan and each record by Anita are sold at $110 and $95 respectively.
How many records
a) by Alan has the shop sold
b) by Anita has the shop sold
set Alan sold x records Anita sold y records
  1. x+y=129
  2.110x+95y=12615
1*110-2 => 15y=1575
            => y=105
                 x=129-105=24...

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簡單的二元一次求解：
1.Ｘ＋Ｙ＝１２９
2.１１０Ｘ＋９５Ｙ＝１２６１５
解出來就是答案了．．．

x+y=129...............(1)
110x+95y=12615.....................(2)
(1)*110-(2)
15y=1575
y=105
x=24
(a)105 records have been sold by Alan
(b) 24 records have been sold by  Anita

free_520

x+y=129
110x+95y=12615
將上面兩式聯立
求出X,Y解為
x=24
y=105

所以答案為
(a)105 records have been sold by Alan
(b) 24 records have been sold by  Anita

[b]回復 [url=http://www04.eyny.com/redirect.php?goto=findpost&pid=196742662&ptid=6970012]1#[/url] [i]daoloi[/i] [/b]


    Ｘ＋Ｙ＝１２９
    １１０Ｘ＋９５Ｙ＝１２６１５
     聯立解即為答案