原式=﹙x-1﹚﹙x²+x+1﹚/﹙x+1﹚﹙x²+x+1﹚+﹙x+1﹚﹙x²-x+1﹚/﹙x-1﹚﹙x²-x+1﹚-2﹙x²+1﹚/﹙x²-1﹚
=﹙x-1﹚/﹙x+1﹚+﹙x+1﹚/﹙x-1﹚-2﹙x²+1﹚/﹙x²-1﹚
=2﹙x²+1﹚/﹙x²-1﹚-2﹙x²+1﹚/﹙x²-1﹚
=0.
原式=﹙x-1﹚﹙x²+x+1﹚/﹙x+1﹚﹙x²+x+1﹚+﹙x+1﹚﹙x²-x+1﹚/﹙x-1﹚﹙x²-x+1﹚-2﹙x²+1﹚/﹙x²-1﹚
=﹙x-1﹚/﹙x+1﹚+﹙x+1﹚/﹙x-1﹚-2﹙x²+1﹚/﹙x²-1﹚
=2﹙x²+1﹚/﹙x²-1﹚-2﹙x²+1﹚/﹙x²-1﹚
=0.