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Nối B với N
Xét tam giác BNC và NMC
- Chung chiều cao hạ từ đỉnh N xuống BC
- MC = 3 lần BC
=> SNMC = 3 lần SBNC = 15 X 3 = 45 ( cm2 )
Xét 2 tam giác ABC và BNC
- Chung chiều cao hạ từ đỉnh B xuống cạnh AC
- NC = 3 lần AC
=> SABC = SBNC X 3 = 45 X 3 = 135 ( CM2 )
Đáp số : 135 cm2
Câu:1 Vì AM=MB , AN=NC
Nên diện tích tam giác AMN=2ABC
=> Diện tích tam gác AMN = 180:2 = 90
...dừng ấn đọc tiếp nhé,ghe rợn lắm,huhu.................................................................................<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<.??????????????? >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>><<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>bố mày đã bảo cấm ấn đọc tiếp rồi mà,dell nghe.NGU
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>cON CHÓ DẠI
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SBNC = 1/4SABC => SABN = 3/4SABC
SNBM = 1/3SABN = 1/3 x 3/4SABC = 1/4SABC
Suy ra :
SBMNC = SBNC + SNBM = 1/4SABC + 1/4SABC = 1/2SABC
Diện tích hình tam giác ABC là :
120 : 2 = 240 (cm2)
Nối B với N
Xét tam giác BNC và NMC
- Chung chiều cao hạ từ đỉnh N xuống BC
- MC = 3 lần BC
=> SNMC = 3 lần SBNC = 15 X 3 = 45 ( cm2 )
Xét 2 tam giác ABC và BNC
- Chung chiều cao hạ từ đỉnh B xuống cạnh AC
- NC = 3 lần AC
=> SABC = SBNC X 3 = 45 X 3 = 135 ( CM2 )
Đáp số : 135 cm2