Question

Sum of first n natural numbers is given by n(n-1)

Answer 1

Answer:

No it is given by n(n+1) /2

PROOF:

As these terms 1 to n are in A. P.

so a=1, t=n, d=1.

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

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

=n(n+1) /2.

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