(x+1)-[(x+3)/(x^2-1)]*[(x^2+1)/(x^2+4x+3)]
=(x+1)-[(x+3)/(x+1)(x-1)]*[(x^2+1)/(x+1)(x+3)]
=(x+1)-[1/(x+1)(x-1)]*[(x^2+1)/(x+1)]
=(x+1)-(x^2+1)/[(x+1)^2*(x-1)]
=[(x+1)^3*(x-1)]/[(x+1)^2*(x-1)]-(x^2+1)/[(x+1)^2*(x-1)]
通分后,分子上：
[(x+1)^3*(x-1)]-(x^2+1)
=[(x+1)^2*(x^2-1)]-(x^2+1)
=(x^2+2x+1)*(x^2-1)-(x^2+1)
=x^4-1+2x(x^2-1)-x^2-1
=x^4+2x^3-x^2-2x-2
好像不能化简了吧