質問: 0$ the rank of the matrix is 3, If $c-b-2d \neq 0$ the rank of the matrix is 4 This is my answer, am I correct here? I feel it is not enough for an answer. Is there anything I have to do? Any advice would be appreciated.
回答: Guide: Your idea is fine. The question is what is the rank of the matrix, the answer should be a number, of which you have not provided. Consider two cases: * $c-b-2d=0$. * $c-b-2d \ne 0$.