A.Maths. Exam

細薯

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 ]

細薯

HELP!!!!!!!!!!!!!!!!!!!!!!!![E-Ah][E-Ah]

oscar

Completing square?

細薯

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 ]

Echo21

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？

細薯

Echo21  在 2004-10-27 06:11 PM 發表:

那些表情符號是什麼來的？

this~~

                               
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Echo21

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？

Echo21

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 ]

抹茶可樂

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

itphone