Let $A$ be set of all $3\times 3$ symmetric matrices all of whose entries are either $0$ or $1.$ Five of these entries are $1$ and four of them are $0$, Then

In a third order matrix $A, a_{ij}$ denotes the element in the $i^{\mathrm{th}}$ row and $j^{\mathrm{th}}$ column.

If $a_{ij}=0$ for $i=j$
        $=1$ for $i>j$
        $=-1$ for $i<j$

Then the matrix is

Let $A=\left[a_{ij}\right]$ is a square matrix of order $2$ where $a_{ij}=i^2-j^2$. Then $A$ is