多项式加减运算其实就是合并同类项。
2x2 - 3x + 1
+ -3x2 + 5x - 7
____________________
-x2 + 2x - 6
2x2 + 0x + 1
+ -3x2 + 5x - 7
____________________
-x2 + 5x - 6
2x2 - 3x - 1
- -3x2 + 5x - 7
____________________
5x2 + 2x +6
2x2 + 0x - 1
- -3x2 + 5x - 7
____________________
5x2 - 5x + 6