Question

write the sum of first n natural numbers

Answer 1

The series is like
1,2,3,4,5,6,..........................,n

as we know,
this is an AP

so using the sum of AP

S = n/2 ( a + l )

S-sum of AP
n-total terms of AP
a-first term of AP
l-last term of AP

S = n/2 ( a+ l )

S= n/2 ( 1 + n) .........substitute all values

S = n ( n + 1 ) / 2 ..........we get the equation

$s = \frac{n(n + 1)}{2}$
is the required equation...............

hope you have understood
if you have any doubt reply me back I will solve your doubts

Answer 2

Answer:

Step-by-stepsn=n/2(2a+(n-1)d)

sn=n/2(2*1+(n-1)*1)

sn=n/2(2+n-1)

sn=n/2(n+1)

hope it will help u