∫ x(sin2x-sinx) dx
= ∫ xsin2x dx - ∫ xsinx dx
= -1/2∫ xdcos2x + ∫ x dcosx
= -1/2(xcos2x - ∫ cos2x dx) + xcosx - ∫ cosx dx
= -1/2(xcos2x - sin2x/2) + xcosx - sinx+C
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