先拆项
x^4/(1-x^4)=-(1-x^4-1)/(1-x^4)=-1+1/(1-x^4)
=-1+1/(1-x²)(1+x²)
=-1+[1/(1-x²)+1/(1+x²)]/2
=-1+[1/(1-x)(1+x)+1/(1+x²)]/2
=-1+[1/(1-x)+1/(1+x)]/4+1/[2(1+x²)]
所以
原式=∫{-1+[1/(1-x)+1/(1+x)]/4+1/[2(1+x²)]}dx
=-x+[-ln|1-x|+ln|1+x|]/4+(1/2)arctanx+C
根据需要你可以再化简。