Please stop posting answers when you are making only comments.
In what you claim to have tried:
A=[-3 6 -1 1 7;1 -2 2 3 -1;2 -4 5 8 -4]
the matrix A has rank 3.
So there is NO matrix you can multiply A with on the left except for the all zero matrix, and get a result of all zeros. That is, there does not exist a non-zero matrix X, such that the product X*A will be entirely zero. This is provable using basic linear algebra.
We can find a non-zero matrix Y such that A*Y will be all zeros. But that was not the question you seem to have posed. Thus...
So effectively zero to with floating point precision. If you want an exact solution, since A is composed of integers, we can find one easily enough. Thus...