[GCSE] 數題一條

dolphin_ice

想問以下個答案係咪y=0?

(4/2y-1) - (1/3y+1) =5 (好似係咁﹐唔係幾記得)
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頭先會考完 Maths, 初頭計左1, 發覺計錯。

之後計到極多(30y)square - 15y =0,
之後唔知點計落去...於是刪晒去寫左y=1 @@|||

6分就係咁樣冇左 [E-Ah] (全卷100滿)

efvjeu

(4/2y-1)-(1/3y+1) =5
(2/y-1)-(1/3y+1)=5
(2-y)-(1/3+y)=5y
(6-3y)-(1+3y)=15y
5=21y
y=5/21

dolphin_ice

Originally posted by efvjeu at 2005-6-15 06:45 PM:
(4/2y-1)-(1/3y+1) =5
(2/y-1)-(1/3y+1)=5
(2-y)-(1/3+y)=5y
(6-3y)-(1+3y)=15y
5=21y
y=5/21

4/2y-1 <--加減唔係唔可以約ga咩? [E-QuM]

細薯

通分再 solve quadratic equation

(4/2y-1) - (1/3y+1) =5

4(3y+1) - (2y-1) / (2y-1)(3y+1) =5
12y+4-2y+1 =5(2y-1)(3y+1)
10y+5 =5(6y^2 -y -1)
10y+5 =30y^2 -5y -5
30y^2 - 15y -10 =0
6y^2 - 3y -2 =0

Originally posted by 紅唇娃 at 2005-6-15 05:53 PM:
想問以下個答案係咪y=0?

(4/2y-1) - (1/3y+1) =5 (好似係咁﹐唔係幾記得)

如果係
(4/2y-1) - (1/3y+1) = -5

answer就有y=0啦

[ Last edited by smallpotato226 on 2005-6-16 at 01:28 PM ]

碧咸

y=0的話
1/3y咪係1/0
係有問題

細薯

Originally posted by 碧咸 at 2005-6-16 02:16 PM:
y=0的話
1/3y咪係1/0
係有問題

1/3y+1 係 1 over 3y+1

dolphin_ice

Originally posted by smallpotato226 at 2005-6-16 01:25 PM:
通分再 solve quadratic equation

哎呀!係喎!

我好蠢呀~~~~~~[E-Ah]

細薯

Originally posted by 紅唇娃 at 2005-6-16 02:53 PM:

哎呀!係喎!

我好蠢呀~~~~~~[E-Ah]

我今日 g math Exam 所以做過類似的

PS: 希望今次Math.有90%分.......><

dolphin_ice

Originally posted by smallpotato226 at 2005-6-16 03:02 PM:

我今日 g math Exam 所以做過類似的

PS: 希望今次Math.有90%分.......><

努力啦!

我諗我maths 70幾掛 @@|||

20030311

y= 0.879 or -0.379