趣味的數學-62

轎車位於A點，貨車位於B點。轎車的速度是貨車的x倍。

如果兩車分別同時從A點和B點出發，轎車追趕上貨車的時間，是它們互相對開後相遇的時間的x倍。

求x。

【改編自 The American Mathematical Monthly，1960，problem E1386】

【原文】

In overtaking a freight, a passenger train, which is x times as fast, takes x times as long to pass as it takes the two trains to pass when going in opposite directions.

Find x.