石块A自塔顶*落下x1时,石块B自离塔顶x2处*落下,两石块同时落地,则塔高( )A.x1+x2B.(x1+x2)^2/(4x1)C.x2/[4(x1+x2)]D.(x1+x2)^2/(x1-x2)要讲理由

问题描述:

石块A自塔顶*落下x1时,石块B自离塔顶x2处*落下,两石块同时落地,则塔高( )
A.x1+x2
B.(x1+x2)^2/(4x1)
C.x2/[4(x1+x2)]
D.(x1+x2)^2/(x1-x2)
要讲理由