১.
$1+3+5+\ldots+(2 n-1)=$ কত?
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$\frac{\mathrm{n}(\mathrm{n}+1)}{2}$
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$\frac{(\mathrm{n}+1)(\mathrm{n}-1)}{\mathrm{n}}$
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$\left\{\frac{\mathrm{n}(\mathrm{n}+1)}{2}\right\}^2$
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$\mathrm{n}^2$
ব্যাখ্যা
$1+3+\cdots+(2n-1)=n^2$।