maths Q F.2

(a-2b+3c)(a+2b-3c)
=[a-(2b-3c)][a+(2b-3c)] Let 2b-3c=b
=(a-b)(a+b)
=a²-b²
=a²-(2b-3c)²
=a²-[(2b)²-2(2b)(3c)+(3c)²]
=a²-(4b²-12bc+9c²)
=a²-4b²+12bc-9c²
(最傳統計法)
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第一位回答的小朋友,,,
贈你–個字''勁''-3-
(a-2b+3c)(a+2b-3c)
=(a-2b+3c)²
甘都俾你計到
第3位: 識就答la...

(a-2b+3c)(a+2b-3c)=
=[a-(2b-3c)][a+(2b-3c)]
=a^2-(2b-3c)^2
=a^2-(4b^2-12cb+9c^2)
=a^2 - 4b^2 - 9c^2 + 12cb

(a-2b+3c)(a+2b-3c)
= a(a+2b-3c)-2b(a+2b-3c)+3c(a+2b-3c)
= a^2+2ab-3ac-2ab-4b^2+6bc+3ac+6bc-9c^2
= a^2-4b^2-9c^2+12bc
= a^2-4b^2-3c(3c+4b)(finish..........囧|||)

吾知岩吾岩........吾記得啦!!!希望岩啦!!!SOR呀.......

2008-12-10 21:20:10 補充：
上面果位朋友........好..........XX =]
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