18/09/16 19:43:53.55 MIF83oNx.net
# 歩行時間:t
# 歩行速度:w
# 迎えの車速:v0
# 同乗の車速:v1
# 出発時刻差:s
# 到着時刻差:X
# l=wt
# 通常走行時間:d/v0+d/v1
# 早退時走行時間:(d-wt)/v0+(d-wt)/v1
# d/v0+d/v1 - ((d-wt)/v0+(d-wt)/v1)= X
# wt(1/v0+1/v1) = X
#
# s0+s+d/v1 - {s0+t+(d-wt)/v1}= X
# s - t(1-w/v1) = X
#
s = t + wt/v0
t = sv0/(v0+w)
X = tw(1/v0+1/v1) = sv0/(v0+w)*w(1/v0+1/v1)