Final answer:
When performing elementary row operations on a matrix, the resulting matrix is found by subtracting half of each element in the first row from the corresponding element in the second row. The correct answer is (b) A - 1/2R1.
Step-by-step explanation:
When performing elementary row operations on a matrix, any row can be multiplied by a non-zero constant and added to another row. In this case, the operation R2 - 1/2R1 means that the second row should be subtracted by half of the first row.
To find the resulting matrix, subtract half of each element in the first row from the corresponding element in the second row. The resulting matrix will have the same elements as matrix A, except for the second row which will have each element subtracted by half of the corresponding element in the first row.
Therefore, the correct answer is (b) A - 1/2R1.