1)MN//BC,△AMN与△ABC相似,AM:AB=AN:AC ,AN=AM*AC/AB=6x/8=3x/4,
△AMN的面积S=1/2*x*3x/4=3x^2/8
2)⊙O的直径=5x/4,半径=5x/8
(8-x):10=5x/8:6
x=192/49
1)MN//BC,△AMN与△ABC相似,AM:AB=AN:AC ,AN=AM*AC/AB=6x/8=3x/4,
△AMN的面积S=1/2*x*3x/4=3x^2/8
2)⊙O的直径=5x/4,半径=5x/8
(8-x):10=5x/8:6
x=192/49