这个需要逐步通分.合并
【1/(x-1)】-【1/(x+1)】 -【2/(x^2+1)】+【4/(x^4+1)】
=(x+1)/(x²-1) -(x-1)/(x²-1) -【2/(x^2+1)】+【4/(x^4+1)】
=2/(x²-1)-【2/(x^2+1)】+【4/(x^4+1)】
=2(x²+1)/(x^4-1)-2(x²-1)/(x^4-1) +4/(x^4+1)
=4/(x^4-1)+4/(x^4+1)
=8x^4/(x^8-1)