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標題: F4 MATHS sum and product of root,幫幫手 [打印本頁]

作者: ~笨東~ 時間: 12-3-25 08:06 PM 標題: F4 MATHS sum and product of root,幫幫手

Give that α+1 and β+1 are the roots of the quadratic equation

x^2+3x-2=0

(a)Find the values of α^2β^2 and α^2+β^2

幫幫手,,,,我GET唔到咩係 α+1 and β+1 are the roots

作者: 〞kIu﹑ 時間: 12-3-25 08:08 PM

so sad 唔識,幫你唔到

作者: 小鴇乂 時間: 12-3-25 08:14 PM

a x^2 -  b x + c

abc are constant coefficient of x^2 & x

sum of roots = b(留意係-唔係+,即係如果ax^2+bx+c,sum of roots 就係-b)
product of roots= c

以上係要背既。

α^2β^2=(αβ)^2=(-2)^2= 4

α^2+β^2=  α^2[+2αβ] +β^2 [ - 2αβ] < [] 入面係要自己加既野,喱個technique都要識
            =  α^2+2αβ +β^2 - 2αβ
            =(a+β)^2 - 2αβ
            =(-3)^2 - 2(-2)
            =9+4 = 13

作者: 小鴇乂 時間: 12-3-26 11:22 PM

回覆小鴇乂的帖子

係wo=,=

a+b = -5
ab=2

再代番入去~~

作者: 小鴇乂 時間: 12-3-26 11:23 PM

回覆小鴇乂的帖子

a+1+b+1=-3
ab+a+b+1=-2

作者: 乂緋夜月乂 時間: 12-3-26 11:23 PM

我中中
睇唔明英中d數

作者: 沙漠之狐~ 時間: 12-3-26 11:42 PM

根和根積!?

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