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標題: equations 一問* [打印本頁]

作者: 小霞的fans 時間: 16/2/2009 06:42 PM
標題: equations 一問*
suppose a graph of y=-x^2+6x-10 is given. write down the equations of the straight lines that should be added in order to solve the following wquations.

a)x^2-6x+5=0

我唔明點計呀 ,, 點解y會=-5既 ??

我係將-x^2+6x-10+2x^2-12x15

y=2x^2+12x+15 .. 點解唔係呢個架 >< ..

y=-5 都算係equation ?

作者: sapphire 時間: 16/2/2009 06:58 PM
y = -x^2 + 6x - 10
0 = x^2 -6x + 5
add the 2 equations, the answer is y = -5.
In order to solve the equation, an equation y = -5 is needed.
The solution of this quadratic equation is the interceptions of this 2 lines.

y = -5 is also equation of horizontal line.

作者: 小霞的fans 時間: 16/2/2009 07:31 PM

原帖由 sapphire 於 15/2/2009 10:58 PM 發表

 登錄/註冊後可看大圖

y = -x^2 + 6x - 10
0 = x^2 -6x + 5
add the 2 equations, the answer is y = -5.
In order to solve the equation, an equation y = -5 is needed.
The solution of this quadratic equation is the intercept ...

y=-5 可以畫到條線嗎 ?唔係得１點咋咩 ?

作者: simon199392 時間: 16/2/2009 07:42 PM
y=-5是一條橫線掃過去,
基本上會同個curve有兩個交點

作者: 雪貓 時間: 17/2/2009 08:16 PM

原帖由 小霞的fans 於 16/2/2009 07:31 PM 發表

 登錄/註冊後可看大圖

y=-5 可以畫到條線嗎 ?唔係得１點咋咩 ?

不論x等於多少,y都是等於-5,所以是一條橫的線

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