So, for example, if we're to hold the time constant, this makes it a lot simpler of an equation, because what we can end up doing is actually crossing out this whole term here.

比如说，如果我们把时间,定为常数，这使得方程,大大简化，因为我们可以把,这一项划掉。

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You can call that your origin.

你也可以把这里定为原点

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