y=(x+m)(-x+2m)
A(-m,0) B(2m,0)
C(m,4m^2 )
D(0.5m ,2m^2)
BD:y=-4mx/3+8m^2/3
AC:y=2mx+2m^2
E(0.2m,2.4m^2)
三角形CDE:0.2m^3=8/5
m=2
抛物线y=-x^2+2x+8
BE:y=-8x/3+32/3
y=(x+m)(-x+2m)
A(-m,0) B(2m,0)
C(m,4m^2 )
D(0.5m ,2m^2)
BD:y=-4mx/3+8m^2/3
AC:y=2mx+2m^2
E(0.2m,2.4m^2)
三角形CDE:0.2m^3=8/5
m=2
抛物线y=-x^2+2x+8
BE:y=-8x/3+32/3