中三數學 (16Q)

= =?你懶得做定唔識做

1. 9(2x＋1)^2＋6(2x＋1)－8
= 36 x^2 +36x +9+12+6-8
=36x^2+48x+7
=(6x+7)(6x+1)

2. 60a^2－4ab－45b^2
=(6a+5b)(10a-9b)

3. 12h^2－36hk＋27k^2
=(2h-3k)(2h-3k)

4. 30a^2－8ab－8b^2
=(5a+2b)(3a-2b)

5. 6ax^2＋11axy－21ay^2
= a( 6x^2+11xy+21y^2)
= a(x+3y)(6x-7y)

6. 2x(3x－7y)＋3y(5y－3x)
=6x^2-14xy+15y^2-9xy
=6x^2-23xy+15y^2
=(6X-5y)(X-3y)

7. 2x^3y＋40x^2y^2＋50xy^3 <-----------你打錯正負?因式解不到
=2xy(x^2+20xy+25y^2)

8.m^2－7/3mn－2n^2
=3m^2-7mn-6n^2
=(3m+2n)(m-3n)

16. a^3＋8b^3＋a^2－4b^2
= (a+2b)(a^2-2ab+4b^2)+(a+2b)(a-2b)
= (a+2b)〔(a^2-2ab+4b^2)+(a-2b)〕

2014-10-02 19:19:40 補充：
9. 16x^2－8xy＋3/4y^2
=(64x^2-32xy+3y^2)
=(8x-y)(8x-3y)

2014-10-02 19:31:18 補充：
7. 8x^3y＋40x^2y^2＋50xy^3
=2xy(4x^2+20xy+25y^2)
=2xy(2x+5)(2x+5)
=2xy(2x+5)^2

2014-10-02 19:44:34 補充：
你自己諗下-0-

2014-10-04 14:17:12 補充：
10. 9(4a＋b)^2＋24(4a＋b)＋16
= 9(16a^2+8ab+b^2)+24(4a+b)+16
=9(4a+b)^2 +24(4a+b)+16

設(4a+b)為 x
9x^2+24x+16
=(3x+4)^2

把x代入(4a+b)
∴= 〔3(4a+b)+4〕^2
=(12a+3b+4)^2

2014-10-04 14:23:37 補充：
11. a^2－2ab＋b^2＋6(a－b)＋9
=(a-b)^2+6(a-b)+9
=(a-b)(a-b+6+9)
=(a-b)(a-b+15)

2014-10-04 14:29:58 補充：
12. x^4－13x^2＋36
=(x^2)^2 -13x^2+36

設(x^2)為 a
a^2-13a+36
=(a-4)(a-9)

把a代入(x^2),
(x^2-4)( x^2-9)
=(x+2)(x-2)(x+3)(x-3)

2014-10-04 14:31:05 補充：
13. 9a^4－52a^2＋64

同上方法

2014-10-04 14:47:47 補充：
14. 2p^6－128
=2〔(p^2)^3 -64)
=2〔(p^2)^3 -4^3)

設(p^2)為 a
2(a^3 -4^3)
=2(a-4)(a^2+4a+16)

把a代入(p^2)
2(p^2-4)(p^4+4p^2+16)
=2(p-2)(p+2)(p^4+4p^2+16) <-----------(p^4+4p^2+16)沒得再化了

2014-10-04 14:56:26 補充：
16. a^3＋8b^3＋a^2－4b^2
=(a+2b)(a^2-2ab+4b^2)+(a+2b)(a-2b)
= (a+2b)〔a^2-2ab+4b^2+a-2b)

2014-10-04 15:01:35 補充：
15. y^6－7y^3－8
=(y^3)^2-7y^3-8

設y^3為a
a^2-7a-8
=(a+1)(a-8)

把a入(y^3)
(y^3+1)(y^3-8)
再化簡= =

2014-10-04 15:05:19 補充：
其實好簡單!!識做的話,你自己做都快過打出來la~