Question

The sum of first n natural number is ​

Answer 1

Answer:

(n)(n+1)/2

Step-by-step explanation:

the first n natural numbers are in A.P. with a1 is 1 and d is 1

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

= n/2(2+n-1)

= n.(n+1)/2

Answer 2

Answer:

Step-by-step explanation:

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

is the required equation