中二數學(三題)!!!!唔識

2011-09-13 9:07 pm

1.Write down two sets of values of a ，b，c，d and e under which the following identity holds.(ax+2)(x2+bx+c) ≡ax3+dx2+e

2a.Factorize 9x2+12xy+4y2
2b.By using the results of (a) ,factorize 9x2+12xy+21y2

3a.Factorize -m2+(r-1)+m-m2

3b.Factorize m(r-1)2-(r-1)-m(1-r)

3c.By using the results of (a)&(b),factorize
[-m2(r-1)+m-m2]+[m(r-1)2-(r-1)-m(1-r)]

更新1:

No.3!!???

更新2:

No.2b嘅答案係3(3x+7y)(x-y)!!!!但係我唔知步驟係咩??

回答 (2)

用戶19657

2011-09-13 9:35 pm

✔ 最佳答案

1
(ax+2)(x2+bx+c) ≡ax3+dx2+e
L.H.S.=ax3 +abx2+acx+2x2+2bx+2c
= ax3 +(ab+2)x2+(ac+2b)x+2c

by comparison of the coefficient,
ab+2 =d
ac+2b=0
2c=e

2
9x2+12xy+4y2
=(3x)2+(2)(3)(2)xy+(2y)2
=(3x+2y)2

2
9x2+12xy+21y2
by a,
=(3x+((21)^0.5)y)2

👍 0 👎 0

[匿名]

2011-09-13 11:04 pm

1
(ax+2)(x2+bx+c) ≡ax3+dx2+e
L.H.S.=ax3 +abx2+acx+2x2+2bx+2c
= ax3 +(ab+2)x2+(ac+2b)x+2c
by comparison of the coefficient,
ab+2 =d
ac+2b=0
2c=e
2
9x2+12xy+4y2
=(3x)2+(2)(3)(2)xy+(2y)2
=(3x+2y)2
2
9x2+12xy+21y2
by a,
=(3x+((21)^0.5)y)2

👍 0 👎 0

收錄日期: 2021-04-23 20:22:44
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20110913000051KK00348

檢視 Wayback Machine 備份