Some important formulae

Formulae:-

1. 1+2 +3+4+...........n=n(n+1)/2.

Ex:-1+2+3+4+5+6+7+8=8(8+1)/2=36

2. 2+4+6+8+..........n terms=n(n+1)

Ex:-2+4+6+8+10+12+14=7(7+1)=56.

3. 1+3+5+7+..........n terms=n²

Ex-1+3+5+7+9+11+13+15+17=9²⁼81