I have a simple sheet:
A | B | C
1: 5 | 4 | =A1+B1
2: 5 | 4 | =A2+B2
3: 5 | 4 | =A3+B3


when i insert a row before line no 2.
A | B | C
1: 5 | 4 | =A1+B1
2:
3: 5 | 4 | =A3+B3
4: 5 | 4 | =A4+B4

i want C2 have formula: =A2+B2 automatically. but i can't.
please tell me how to make it?