On 9/6/99, downeyad asks about Q5 of MA322-005,Section 2.3 2.4 and 2.5: please go over this in class. Response:  form the augmented matrix  and carry out the elimination.  The last row is 0 0 0 a.   If a is not zero there is no solution.

On 9/11/99, moeyli  and tehwi ask  about Q12 of MA322-005,Section 2.3 2.4 and 2.5(Sept. 14): Please explain in class  Response:   Hint:  Check if you can multiply first. Then check if you can add.

On 9/11/99, moeyli  and tehwi ask about Q16 of MA322-005,Section 2.3 2.4 and 2.5(Sept. 14): Please explain in class.  Response:   Hint: Write down a 2 by 2 diagonal matrix and multiply it times some 2 by 3 or 2 by 4 matrix and try to figure out which of the alternatives is correct.

On 9/12/99, mitchema1 asks about Q5 of MA322-005,Section 2.3 2.4 and 2.5(Sept. 14): The system seems to say 5(x1)+7(x2)+9(x3)=4(x1)+4(x2)+4(x3)=1 Response: Yes. These are two of the 3 equations in the system. There are solutions to these two: for example x3 = 0, x1 = 3 and x2 = -2. However, with the top equation thrown in, there are no solutions if a is not 0.

On 9/13/99, nelsonca asks about Q1 of MA322-005,Section 2.3 2.4 and 2.5(Sept. 14): But wouldn't this mean you're adding to row two not subtracting? I thought the point was to make it zero? Response: You add a -2*row1 to row2 to eliminate the 6 in the 2,1 position. That's what the first elimination matrix does. This can also be thought of as subtracting 2*row1 from row2, but the effect is the same.

On 9/13/99, kendigbr asks about Q18 of MA322-005,Section 2.3 2.4 and 2.5(Sept. 14): Unfortunately, unless I'm making a huge mistake I get both answers to work as inverse. Response: Huge mistake. A times the first alternative is [-1 0] for the first row and [0, -9] for the second row.