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[minhdat881439]

Cho tứ giác ABCD. Xét M là điểm tùy ý, gọi P, Q, R, S thỏa:

$\underset{MB + }{\rightarrow}$$\underset{MC + }{\rightarrow}$$\underset{MD}{\rightarrow}$$\underset{=4MP}{\rightarrow}$
$\underset{MC+}{\rightarrow}$$\underset{MD+}{\rightarrow}$$\underset{MA}{\rightarrow}$$\underset{=4MQ}{\rightarrow}$
$\underset{MD+}{\rightarrow}\underset{MA+}{\rightarrow}\underset{MB}{\rightarrow}\underset{=4 MS}{\rightarrow}$
$\underset{MA+}{\rightarrow}$$\underset{MB+}{\rightarrow}$$\underset{MC}{\rightarrow}$$\underset{=4MS}{\rightarrow}$
Tìm M sao cho: PA=QB=RC=SD

Edited by minhdat881439, 12-04-2012 - 19:50.