2(x^2+1)/(x+1)+6(x+1)/(x^2+1)=7
2(x^2+1)^2+6(x+1)^2=7(x+1)(x^2+1)
2(x^2+1)^2-7(x+1)(x^2+1)+6(x+1)^2=0
[2(x^2+1)-3(x+1)][(x^2+1)-2(x+1)]=0
2x^2-3x-1=0或x^2-2x-1=0
x1=(3+√17)/4,x2=(3-√17)/4,x3=1+√2,x4=1-√2