有点模糊，不过不打紧
换元t=√x，dx=2tdt=∫(0到2)2(t²+3)/(2-t²)dt=∫10/(2-t²)-2dt=10/2√2∫1/(√2+t)+1/(√2-t)-2dt=(5/√2)(ln(√2+t)-ln(√2-t))-2t
