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