∫ x²lnx dx= ∫ lnx d(x³/3)= (1/3)x³lnx - (1/3)∫ x³ dlnx,分部积分= (1/3)x³lnx - (1/3)∫ x³ • 1/x dx= (1/3)x³lnx - (1/3)∫ x² dx= (1/3)x³lnx - (1/3)(...