Question:
The sum of first n odd natural numbers is
(a) 2n +1
(b) n2
(c) n2 –1
(d) n2 +1
Solution:
(b) Sum of first $n$ odd natural numbers $=\Sigma(2 n-1)=2 \Sigma n-n$
$=\frac{2 \times n(n+1)}{2}-n=n(n+1)-n=n^{2}+n-n=n^{2}$
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