Question

please solve it
please​

Answer 1

Step-by-step explanation:

'n' natural njmbers = 1,2,3,4,5,.......n times

d=2-1=1

a=1

Sn=n/2{2a+(n-1)d}

=n/2{2×1+(n-1)×1}

=n/2(2+n-1)

=n/2 ×(n+1)

={n(n+1)}/2 Answer