a/ $S1$=$S2+S3$
b/$\frac{AF}{FN}+\frac{BF}{FM}+\frac{CE}{EM}+\frac{DE}{EN}\geq 4$
Edited by Nguyen Duc Nghia, 30-05-2012 - 21:49.
Edited by Nguyen Duc Nghia, 30-05-2012 - 21:49.
Nguyễn Đức Nghĩa tự hào là thành viên VMF
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