计算不定积分∫x^21n xdx

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计算不定积分∫x^21n xdx
计算不定积分∫x^21n xdx

计算不定积分∫x^21n xdx
∫x²lnx dx,宜用分部积分法
= (1/3)∫lnx d(x³)
= (1/3)x³lnx - (1/3)∫x³ d(lnx)
= (1/3)x³lnx - (1/3)∫x² dx
= (1/3)x³lnx - (1/9)x³ + C
= (1/9)x³(3lnx-1) + C

不可积。 设t=3∧x/e∧x,则lnt=x*ln(3/e),x=lnt/ln(3/e). ∫3∧x/e∧xdx =∫(3/e)^xdx =(3/e)^x/(ln3-1) +c