导数一题.(xlnx)'=f(x)如图划红线部分,用凑微分法,怎么把 xlnx 弄没了?
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导数一题.
(xlnx)'=f(x)
如图
划红线部分,用凑微分法,怎么把 xlnx 弄没了?
![](http://img.wesiedu.com/upload/7/55/7553a613f9500e03b85b875851f27c46.jpg)
(xlnx)'=f(x)
如图
划红线部分,用凑微分法,怎么把 xlnx 弄没了?
![](http://img.wesiedu.com/upload/7/55/7553a613f9500e03b85b875851f27c46.jpg)
![导数一题.(xlnx)'=f(x)如图划红线部分,用凑微分法,怎么把 xlnx 弄没了?](/uploads/image/z/6625777-49-7.jpg?t=%E5%AF%BC%E6%95%B0%E4%B8%80%E9%A2%98.%EF%BC%88xlnx%29%27%3Df%28x%29%E5%A6%82%E5%9B%BE%E5%88%92%E7%BA%A2%E7%BA%BF%E9%83%A8%E5%88%86%EF%BC%8C%E7%94%A8%E5%87%91%E5%BE%AE%E5%88%86%E6%B3%95%EF%BC%8C%E6%80%8E%E4%B9%88%E6%8A%8A%26nbsp%3Bxlnx%26nbsp%3B%E5%BC%84%E6%B2%A1%E4%BA%86%EF%BC%9F)
∵ df(x) = f'(x)dx
∴ f'(x)dx = df(x)
反过来,
d(xlnx) = (xlnx)'dx ,即 (xlnx)'dx = d(xlnx)
往后就是【分部积分法】了.
∴ f'(x)dx = df(x)
反过来,
d(xlnx) = (xlnx)'dx ,即 (xlnx)'dx = d(xlnx)
往后就是【分部积分法】了.