{ ( x+10)²=xy
{(x+5)(y-9)=xy
thx!!~
一條數學題!
2010-06-18 2:34 am
回答 (1)
2010-06-18 3:49 am
✔ 最佳答案
{ ( x+10)²=xy.....(1){(x+5)(y-9)=xy.....(2)
By(2) :
xy + 5y - 9x - 45 = xy
y = (9x + 45)/5
sub into (1) :
(x+10)² = x(9x + 45)/5 ,
5(x+10)² = x(9x + 45)
5x² + 100x + 500 = 9x² + 45x
4x² - 55x - 500 = 0
(4x + 25)(x - 20) = 0
x = - 25/4
y = (9(-25/4) + 45)/5 = - 9/4
or
x = 20
y = (9(20) + 45)/5 = 45
收錄日期: 2021-04-21 22:12:54
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20100617000051KK01216