Question
Write the sum of first n odd natural numbers.

Answer

We have, 1 + 3 + 5 + ... up to n terms $\therefore\text{S}_\text{n}=\frac{\text{n}}{2}[2\times1+(\text{n}-1)\times2]$ $=\frac{\text{n}}{2}[2+2\text{n}-2]$ $=\frac{\text{n}}{2}\times2\text{n}$ $=\text{n}^2$ $\therefore1+3+5+\ ...$ up to n terms = $n^2$ Hence, sum of first n odd natural numbers is $n^2$.

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