Thursday, August 18, 2011

Remember this

1. (a+b)^2 =a^2 +2ab+b^2
2. (a-b)^2 =a^2 -2ab+b^2
3. (a+b)(a-b)= a^2 -b^2

1 & 2 are linked.
If a=x and b=-y
[x+(-y)]^2 =(x)^2 +2(x)(-y)+(-y)^2
(x-y)^2 = x^2 -2xy+y^2

See the link?

3. (a+b)(a-b)=a^2 +ab-ba+b^2=a^2 -b^2
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Case 1:
xy=2
x+y=4
find x^2 +y^2



Case 2: x-y=3
x+y=6
x^2 -x^2
find -----------
3

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