x³/(x²+1)=(x³+x-x)/(x²+1)=x-x/(x²+1)所以原式=∫(0,5)xdx-∫(0,5)x/(x²+1)dx=∫(0,5)xdx-1/2∫(0,5)d(x²+1)/(x²+1)=x²/2-1/2*ln(x²+1) (0,5)=25/2-ln√26
