明天要交了!!!大家help help ~~F.2 MATH

[匿名]

2010-10-08 2:33 am

大家help help ~~F.2 MATHS

有幾條maths, 希望大家help help (要式) english

Factorize
1) x^6(^係次方)-x^4

2) 25(3x-2y)^2-9(2x+y)^2

3) 12(c^2+2)-2(c^2+2)^2-18

4) a^2-4b^2+12b-9

Find A,B,C values

1) 3(x^2-1)+Ax+15= (b-x)(Cx-2)

thx

回答 (1)

ShikaP

2010-10-08 4:14 am

✔ 最佳答案

Factorize
1) x^6-x^4
=x^4(x^2-x)

2) 25(3x-2y)^2-9(2x+y)^2
=(5)^2(3x-2y)^2-(3)^2(2x+y)^2
=(5(3x-2y))^2-(3(2x+y))^2
=(15x-10y)^2-(6x+3y)^2
=(15x-10y+6x+3y)(15x-10y-6x-3y)
=(21x-7y)(9x-13y)

3) 12(c^2+2)-2(c^2+2)^2-18
=(12-2(c^2+2))(c^2+2)-18
=(12-2c^2+2)(c^2+2)-18
=2(5-c^2)(c^2+2)-18
=2(5-c^2-9)(c^2+2)
=(-14-c^2)(c^2+2)

4) a^2-4b^2+12b-9
=a^2-((2b)^2-2(2b)(3)+3^2)
=a^2-(2b-3)^2
=(a-2b+3)(a+2b-3)

Find A,B,C values

1) 3(x^2-1)+Ax+15= (b-x)(Cx-2)
LHS=
3(x^2-1)+Ax+15
=3x^2-3+Ax+15
=3x^2+12+Ax
RHS
= (b-x)(Cx-2)
=CBx-Cx^2-2b+2x
=(CB+2)x-Cx^2-2b
so A=(CB+2)
C=3
B=6
A=20

2010-10-07 20:35:30 補充：
sor it's
C=-3
b=-6
A=20

2010-10-08 16:18:26 補充：
希望幫到你,,有錯唔好介意

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