∫（x-2）dx/x²+2x+3=?

∫（x-2）dx/x²+2x+3=?

令u=x+1,则du=dx
原式=∫(u-3)du/(2+u^2)
=∫udu/(2+u^2)-∫3du/(2+u^2)
=1/2·ln(2+u^2)-3/√2·arctan(u/√2)+C
=1/2·ln(x^2+2x+3)-3/√2·arctan((x+1)/√2)+C

没看懂题、除是怎么除