Adjacency matrix and detecting a clique.

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There is given a graph $G$ and its adjacency matrix $A(G)$

I ask a quite general question:

Assume that graph $G$ contains a $k$-clique. How does this affect on behaviour of $A(G)$? How to detect a clique in a clever way using $A(G)$?

By writing "clever way" i meant that not to just looking at exemplary matrix, but rather at its properties. Suppose that we have given any adjacency matrix, then deciding whether it has a clique by looking at it is impossible.

So far my idea is following:

Let's consider the part of matrix which is below a diagonal. Let's call it $B$. Then to each column of $B$ we write a sum of the elements in that given column. The same with rows.

Having that values can we determine $B$?

Using that values can we detect a clique in $B$?

Regards.