Final answer:
Matrix b must be a 1x6 matrix to be added to matrix a, which has the same dimensions.
Step-by-step explanation:
The student is asking about the dimensions of matrices that can be added together. When adding two matrices, it is essential that they have the same dimensions. In this case, a is a 1x6 matrix, which means it has one row and six columns. Therefore, for the summation a + b to be computationally possible, matrix b must have the same dimensions as matrix a.
If a is a 1x6 matrix, then matrix b must also be a 1x6 matrix. This means that it has one row and six columns, ensuring the two matrices have the same dimensions and thus can be added together.