Q12 from page 328:

Many students stated that the matrix could be transformed into a diagonal
matrix through row and column operations, without providing a method.  Since
this implies that the matrix can be row reduced to the identity matrix, I
felt such an assumption trivialized the question.  Also, there is not a
unique solution, so the assumption seemed ambiguous.  Also, a few students
erroneously believed that theorems 5.3 and 5.4 were if and only if.

Q8 from page 343:

Most students correctly used the adjoint, but got stuck proving that the
lower elements equaled zero.  Those who did not attempt to draw the general
form had the most difficulty.

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Problem 2 #12 from the text book, no student used induction
like the solution: all showed that row reducing would be easy and that
nonzero elements would appear on the diagonal.
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The assigment was mostly well done.  Question 2 (p328 #12) was done
differently by most students.  Only a few used induction.  Most interchanged
rows and used the fact that it was non-singular to say detA != 0.  There
were some hand-wavy proofs for question 4(p 343 #8).  Many students didn't
justify the fact that the lower entries in adjA are 0 very well (or not at
all).

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