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AX= AX cΔt = ct - cΔt (1)
BX= BX - cΔ t= ct - cΔt, (2)
, :
AX - BX=c(t - t), (3)
:
AX + BX=AB, (4)
(3) (4), :
AX= [AB + c(t - t)] / 2.
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