The column where D is located is linearly independent (it is known that low-dimensional vectors are independent, and it is irrelevant to expand to high dimensions), but all columns of A except D can be linearly represented by the column where D is located (assuming that the r+ 1 order sub-formula containing D is 0), so the rank of the column vector group of A is equal to the number of columns of D, that is, R. And the rank of matrix = column rank = row rank,

So the rank of a is r, then all k (k >; R) order subforms are all zero, and r+2 order is naturally zero.