 Solution

ID: past-exam-of-the-mathematics-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2022/paper-2/2/a/solution

Scalar entries commute, so

B_{jk} A_{ij} = A_{ij} B_{jk}

is exactly the summed entry formula for matrix multiplication. Hence

C = A B .

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