Question

# What is the sum of any two-odd number?

As you know odd number is in the form of $\left( {2n - 1} \right)$ or $\left( {2n + 1} \right)$ (where n = 1, 2, 3…..)
$\Rightarrow$sum of odd numbers is
$\Rightarrow \left( {2n - 1} \right) + \left( {2n + 1} \right)$
$\Rightarrow 2n - 1 + 2n + 1 = 4n$