If a, b are positive integers such that a < b and [a b]

$\left[\begin{array}{ll}a & b\end{array}\right]\left[\begin{array}{l}a \\ b\end{array}\right]=[25]$

$\Rightarrow\left[a^{2}+b^{2}\right]=[25]$

$\Rightarrow a^{2}+b^{2}=25$

Now,

$3^{2}+4^{2}=5^{2}=25$

$\therefore a=3$ and $b=4 \quad(a

Thus, the ordered pair $(a, b)$ is $(3,4)$.

If $a, b$ are positive integers such that $a$(\underline{3}, \underline{4})$