∫2下面1 （2x）/(x+1) dx
=[1,2]∫[2(x+1)-2]/(x+1)dx
=[1,2]∫2-2/(x+1)dx
=[1,2]2x-2ln(x+1)
=(4-2ln3)-(2-2ln2)
=2+2ln2-2ln3