| y+1 |
| x+1 |
| x+1 |
| y+1 |
=
| (y+1)2 |
| (x+1)(y+1) |
| (x+1)2 |
| (y+1)(x+1) |
=
| y2+2y+1 |
| xy+x+y+1 |
| x2+2x+1 |
| xy+y+x+1 |
=
| y2+x2+2(x+y)+2 |
| xy+(x+y)+1 |
=
| (x+y)2-2xy+2(x+y)+2 |
| xy+(x+y)+1 |
把x+y=-2，xy=-1代入上式得：
原式=
| (-2)2-2×(-1)+2×(-2)+2 |
| -1-2+1 |
| y+1 |
| x+1 |
| x+1 |
| y+1 |
| y+1 |
| x+1 |
| x+1 |
| y+1 |
| (y+1)2 |
| (x+1)(y+1) |
| (x+1)2 |
| (y+1)(x+1) |
| y2+2y+1 |
| xy+x+y+1 |
| x2+2x+1 |
| xy+y+x+1 |
| y2+x2+2(x+y)+2 |
| xy+(x+y)+1 |
| (x+y)2-2xy+2(x+y)+2 |
| xy+(x+y)+1 |
| (-2)2-2×(-1)+2×(-2)+2 |
| -1-2+1 |