香港寵物小精靈村落 論壇

標題: A.Maths. Exam [打印本頁]
作者: 細薯    時間: 27/10/2004 04:11 PM
標題: A.Maths. Exam
help!
tomolo A.Math Exam la~~
i have some question don't know how to do!~

help~~~~~~~~~~~

1.Convert the expresion x^2-4n+1 into the form (x+a)^2 +b and write down the values of a and b in terms of n.

[ Last edited by smallpotato226 on 2004-10-27 at 04:12 PM ]
作者: 細薯    時間: 27/10/2004 05:53 PM
HELP!!!!!!!!!!!!!!!!!!!!!!!![E-Ah][E-Ah]
作者: oscar    時間: 27/10/2004 05:53 PM
Completing square?
作者: 細薯    時間: 27/10/2004 05:55 PM
oscar  在 2004-10-27 05:53 PM 發表:

Completing square?

i only know this.....

x^2-4n+1=(x-1)^2

then??

is that

a=1
b=0

?????

++++++++++++++++++++++++++++++++

one more question

if [E-Sad] and [E-Hap] are the roots of the quadratic equation ax^2 + bx+c=0 ,then
ax^2 + bx+c=a(x-[E-Sad])(x-[E-Hap])

i don't understand the red part!

[ Last edited by smallpotato226 on 2004-10-27 at 06:03 PM ]
作者: Echo21    時間: 27/10/2004 06:11 PM
smallpotato226  在 2004-10-27 17:55 發表:

i only know this.....

x^2-4n+1=(x-1)^2

then??

is that

a=1
b=0

?????

++++++++++++++++++++++++++++++++

one more question

if [E-Sad] and [E-Hap] are the roots o ...

那些表情符號是什麼來的？
作者: 細薯    時間: 27/10/2004 06:13 PM
Echo21  在 2004-10-27 06:11 PM 發表:

那些表情符號是什麼來的？

this~~


                               
登錄/註冊後可看大圖
作者: Echo21    時間: 27/10/2004 06:29 PM
if α and β are the roots of the quadratic equation ax^2 + bx+c=0 ,then
ax^2 + bx+c=a(x-α)(x-β)

是不是已經完整的題目？
作者: Echo21    時間: 27/10/2004 06:41 PM
剛剛看了最上樓的題目：
1.Convert the expresion x^2-4n+1 into the form (x+a)^2 +b and write down the values of a and b in terms of n.

答案（未必對）：
     x^2 - 4nx + 1
= (x^2 - 4nx) + 1
= [x^2 - 2(2nx)] + 1
= [x^2 - 2(2nx) + 4n^2] - 4n^2 + 1
= (x - 2n)^2 - 4n^2 + 1

Sub. (x - 2n)^2 - 4n^2 + 1 into (x + a)^2 + b
∴ a = -2n//
　 b = -4n + 1//

完成！

[ Last edited by Echo21 on 2004-10-27 at 07:30 PM ]
作者: 抹茶可樂    時間: 27/10/2004 07:01 PM
I'm afraid you of wrong typing of queation
x^2 -4nx +1
=x^2 -2(x)(2n) +1
=x^2 -2(x)(2n) +(2n)^2 -(2n)^2+1
=(x-2n)^2+1-4n^2

a=-2n
b=1-4n^2
作者: itphone    時間: 27/10/2004 08:12 PM
作者: Echo21    時間: 27/10/2004 08:23 PM
作者: 細薯    時間: 28/10/2004 01:06 PM
落雷  在 2004-10-27 07:01 PM 發表:

I'm afraid you of wrong typing of queation


don't be afraid~
i have typed the correct question!

does anyone have the A.Maths Textbook of the name called "New Trend Additional Mathematics Volume One"??
my question is come from P.6 , Classwork 5

++++++++++++++++++++++++++++++++++++++++++++++
testing

5<SUP>2</SUP>

haha~~funny~qq~XDD

[ Last edited by smallpotato226 on 2004-10-30 at 09:27 AM ]
作者: 抹茶可樂    時間: 29/10/2004 10:46 PM
Let f(x) = (16-k)x^2 +12x -k , where k is a constant.
a) Find the discriminant of f(x)=0 .
b) Find the condition of k such that f(x)≧0 for all real values of x .
作者: fish    時間: 29/10/2004 10:49 PM
smallpotato226  在 2004-10-28 01:06 PM 發表:

don't be afriad~
i have typed the correct question!

does anyone have the A.Maths Textbook of the name called "New Trend Additional Mathematics Volume One"??
my question is come from  ...


afriad＜－－－－afraid ....."
作者: 細薯    時間: 30/10/2004 09:27 AM
fish  在 2004-10-29 10:49 PM 發表:

afriad＜－－－－afraid ....."


改了.......(成日錯><)
作者: Ronald0077    時間: 30/10/2004 05:52 PM
落雷  在 2004-10-29 10:46 PM 發表:

Let f(x) = (16-k)x^2 +12x -k , where k is a constant.
a) Find the discriminant of f(x)=0 .
b) Find the condition of k such that f(x)≧0 for all real values of x .


a) Δ = b<sup>2</sup> - 4ac
       = 12<sup>2</sup> - 4(16-k)(-k)
       = 144 + 64k - 4k<sup>2</sup>

b) As f(x) ≧ 0, Δ ≦ 0 and 16-k ＞ 0
                      144 + 64k - 4k<sup>2</sup>≦0 and k＜16
                      k<sup>2</sup> - 16k - 36 ≧ 0 and k＜16
                      (k - 18)(k + 2) ≧ 0 and k＜16
                      (k ≦ -2 or k ≧ 18) and k＜16
                   ∴k ≦ -2

see if sth wrong @@~



歡迎光臨 香港寵物小精靈村落 論壇 (https://proxy.archiver.hkpnve.pokebeacon.com/)Powered by Discuz! X3.2