Question

The suitable formula to find the sum of first n terms of an Ap 1+3+5+7+...........is

Answer 1

Arithmetic Progression: 1+3+5+7+...........+n

Here first term a=1,difference d =second term - first term = 3-1 = 2

Sum of 'n' terms are:

$S=n/2[2a+(n-1)d]$

Put the value of a and d in the above equation.

$S=n/2[2.1+(n-1)2]$

$S=n/2[2+2n-2]$

$S=n/2[2n]$

$S=n^{2}$