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linhngocc3hv
2 năm trước
Cho `\DeltaABC` có `BC = 2AB`. Gọi `M` là trung điểm của `BC`, `N` là trung điểm của `BM`. Trên tia đối của tia `NA` lấy điểm `E` sao cho `AN = EN`. Chứng minh: `a)` `\DeltaNAB = \DeltaNEM` `b)` `\DeltaMAB` là tam giác cân `c)` `M` là trọng tâm của `\DeltaAEC` `d)` `AB > 2/3 AN`
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