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No. 2
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No. 4
QPD
2005/12/12 10:03
a = (b + 1) + b = 2b + 1
(b + 1)^2 - b^2 = b^2 + 2b + 1 - b^2 = 2b + 1
•ÔM
(b + 1)^2 - b^2 = b^2 + 2b + 1 - b^2 = 2b + 1