它通常由12天指数移动平均数减去26天指数平均数得来。
It is generally calculated by subtracting a 26-day exponential moving average from a 12-day EMA.
注意当价格升高时指数移动平均数有一个更高值，而价格下降时其下降比简单一定平均数更快。
Notice how the EMA has a higher value when the price is rising, and falls faster than the SMA when the price is declining.
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