Question

what is the formula of sum of first n odd numbers

Answer 1

Answer: step by step explanation:

Sn = n/2 (2a + (n-1)d) where a= first term , n= no. of terms , d= difference

In case of odd no.s 1 + 3 + 5+……..+n

a =3 , no. of terms =n and d=2

Putting the values in above formula we get,

Sn = n/2 (2×3 + (n-1)2)

=n/2(6 + 2n-2)

=n/2( 2n+ 4)

=n(n+2)

Or n² + 2n

Therefore the sum is n²+ 2n.