AC中点M BC中点N
2OM=OA+OC 2ON=OB+OC
2OA+3OB+5OC=0
2OA+2OC+3OB+3OC=0
4OM+6ON=0
MON同线
|OM|=2|ON|/3 |MN|=|OM|+|ON|=5|ON|/3
|ON|/|MN|=3/5
Scon=(3/5)Scmn
Sboc=2Scon=(6/5)Scmn=(3/10)Sabc
X=3/10
AC中点M BC中点N
2OM=OA+OC 2ON=OB+OC
2OA+3OB+5OC=0
2OA+2OC+3OB+3OC=0
4OM+6ON=0
MON同线
|OM|=2|ON|/3 |MN|=|OM|+|ON|=5|ON|/3
|ON|/|MN|=3/5
Scon=(3/5)Scmn
Sboc=2Scon=(6/5)Scmn=(3/10)Sabc
X=3/10