
定积分问题求解答
1个回答
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解:
∫xlnxdx
=(1/2)∫lnxd(x²)
=(1/2)x²lnx-(1/2)∫x²(1/x)dx
=(1/2)x²lnx-(1/2)∫xdx
=(1/2)x²lnx-(1/4)x²
带入上下限,有
=[(1/2)e²-(1/4)e²]-[-(1/4)]
=[e²/4]+1/4
=(e²+1)/4
∫xlnxdx
=(1/2)∫lnxd(x²)
=(1/2)x²lnx-(1/2)∫x²(1/x)dx
=(1/2)x²lnx-(1/2)∫xdx
=(1/2)x²lnx-(1/4)x²
带入上下限,有
=[(1/2)e²-(1/4)e²]-[-(1/4)]
=[e²/4]+1/4
=(e²+1)/4
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