Mathes question

👨🏻‍🏫 學術台數學

[匿名]

2013-10-27 1:15 am

2(x^2+3y^2)=xy
and then,find the x/y=?

更新1:

How to divid by y²?

更新2:

but the ans is 2

更新3:

修正問題:2(x^2 - 3y^2)=xy ,then find x/y

回答 (2)

螞蟻雄兵

2013-10-27 4:15 am

✔ 最佳答案

2(x^2+3y^2)=xy and then,find the x/y=?
Sol
Set p=x/y，y<>0
x=py
2(p^2y^2+3y^2)=py^2
2p^2+6=p
2p^2－p+6=0
p=[1+/-√(1－48)]/4
=(1+/-i√47)/4
題目改為
2(x^2－3y^2)=xy andthen，find the x/y=?
Sol
Set p=x/y，y<>0
x=py
2(p^2y^2－3y^2)=py^2
2p^2－6=p
2p^2－p－6=0
(2p+3)(p－2)=0
p=－3/2 or p=2

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用戶4366

2013-10-27 1:45 am

2(x²+3y²)=xy
divid by y²
2[(x/y)²+3] = x/y
2(x/y)² - x/y + 6 = 0

Solve by [-b±√(b²-4ac)]/2a

x/y = [1+(√23)i]/4 or [1-(√23)i]/4

2013-10-27 14:33:31 補充：
這步有問題

2p^2－p－6=0
(2p+3)(p－2)=0
p=－3/2 or p=2

似乎是

2p^2－p－6=0
(2p－3)(p+2)=0
p=3/2 or p=－2

出唔到你要的 answer x/y = 2

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收錄日期: 2021-04-27 20:34:05
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