Question

a 5×7 matrix has all entries equal to one .then the rank of the matrix is​

Answer 1

Step-by-step explanation:

Now i thought because the basis consist of three vectors that the rank was also 3. Because the rank is the dimension of the column space of A and because the basis of A is the column space i thought the answer is 3. But in my book the answer was that the dimension of the null space was 3 and because of that 7 - 3 is 4 and the rank is 4...