 Solution

ID: past-exam-of-the-year-1-of-the-computer-science-course-of-the-university-of-oxford/2021/digital-systems-linear-algebra-introduction-to-formal-proof/5/b/iv/solution

The

j

th column of

A E

A (E e_{j})

e_{1}, e_{2}

and interchanges

e_{3}, e_{4}

, so these columns are

A e_{1}, A e_{2}, A e_{4}, A e_{3}

. They are exactly the first, second, fourth and third columns of

A

. Thus right multiplication by $E$ interchanges columns three and four, leaving the others unchanged.

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