原式=(x+1)/(x²+1)×(x²+1)(x²-1)/(x+1)³-(x-3)/(x+1)=(x²-1)/(x+1)²-(x-3)/(x+1)=(x²-1-x²+2x+3)/(x+1)²=2(x+1)/(x+1)²=2/(x+1)=2/(√3+1+1)=4-2√3