平抛的轨迹方程：y=-1/2gt^2+Cx=vt则得：y=-1/2(g/v^2)x^2+C对A点带入(0,H),(2L,0),得：y=H-(H/4L^2)x^2 ...........1对B点带入(0,2H),(L,0),得：y=2H-(2H/L^2)x^2 ..........21、2联立(y-H)/(y-2H)=1:8y=6H/7
6H/7
