f.2 maths identities.

1.
A + 2 = 2
A = 0
A-B = 5
0-B = 5
B=-5
2.
L.H.S.
=(x-3)^2
=x^2-6x+9
x^2-6x+9≡x+Ax+(A+B)
A = - 6
A+B = 9
-6+B=9
B=14
3.
(-5a-2b)^2
= (5a+2b)^2
= (5a)^2 + 2(5a)(2b) + (2b)^2
= 25a^2 + 20ab + 4b^2
4.
4(3m-8n)^2
=4(9m^2 - 48mn + 64n^2)
=36m^2 - 192mn + 256n^2
5. (a/7 - 5/b)^2
= (a/7)^2 - 2(a/7)(5/b) + (5/b)^2
= a^2 / 49 - 10a/7b + 25/b^2
=

2009-10-12 21:14:30 補充：
5. The answer is a^2 / 49 - 10a/7b + 25/b^2

Please miss out the extra "="

Find the values of A and B in each of the following identities.
1.(A+2)x +(A-B)≡2x+5

A+2=2
A=0
A-B=5

0-B=5
0=5+B
B=-5


2.(x-3)²≡x²+Ax+(A+B)

L.H.S.=(x-3)²=x²-6x+3
A=-3

A+B=3
-3+B=3
B=6



Expand the following expressions.
3.
(-5a-2b)²=-(5a+2b)²=-(25a²+20ab+4b²)=-25a²-20ab-4b²

4.
4(3m-8n)²=4(9m²-48mn+64n²)=36m²-192mn+256n²

5.(a/7 - 5/b)²=a²/49 - (10 a)/(7 b) + 25/b²

2009-10-12 18:32:54 補充：
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http://www.wolframalpha.com/

2009-10-12 20:31:30 補充：
更正:
2.(x-3)²≡x²+Ax+(A+B)

L.H.S.=(x-3)²=x²-6x+3
A=-6

A+B=3
-6+B=3
B=9