F.2 Mathematics!!!

[匿名]

2009-12-25 9:19 pm

Find the values of A and B in the following identities.
(write down the steps)
(2x+5){2}-Ax=4x{2}+16x+(29-2B)

{ }內指次方

Find the values of A.B and C in the following identities.
(write down the steps)
3(x{2}-1)+Ax+15=(B-x)(Cx-2)

{ }內指次方

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最快回答而答案正確將被選為最佳回答

更新1:

重新..... Find the values of A and B in the following identities. (write down the steps) (2x+5)^2-Ax=4x^2+16x+(29-2B) Find the values of A.B and C in the following identities. (write down the steps) 3(x^2-1)+Ax+15=(B-x)(Cx-2) **************************************************************** 最快回答而答案正確將被選為最佳回答

更新2:

to tonyleung052 SORRY ABOUT THAT 你既答案係岩但係唔可以代x=-2,when個題目冇提供x=-2 maybe 我比多個example, 2(x+5)+3(x-1)=Ax+B 2x+10+3x-3=Ax+B 5x+7=Ax+B 所以A=5 B=7

回答 (1)

用戶2053

2009-12-25 10:27 pm

✔ 最佳答案

(2x+5){2}-Ax=4x{2}+16x+(29-2B)

(2x+5)^2 - Ax = 4x^2 + 16x + (29 - 2B)

when x = 0 :

25 = 29 - 2B

B = 2

Becomes (2x+5)^2 - Ax = 4x^2 + 16x + (29 - 2*2)

when x = 1 :

49 - A = 4 + 16 + 29 - 4

A = 4

3(x{2}-1)+Ax+15=(B-x)(Cx-2)

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

when x = 0 :

- 3 + 15 = B(-2)

B = - 6

Becomes 3(x^2 - 1) + Ax + 15 = (- 6 - x)(Cx - 2)

when x = - 6 :

3(36 - 1) - 6A + 15 = 0

6A = 35*3 + 15

A = 20

Becomes 3(x^2 - 1) + 20x + 15 = (- 6 - x)(Cx - 2)

when x = 1 :

0 + 20 + 15 = (- 7)(C - 2)

35/(-7) = C - 2

C = - 3

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