Hi guys,

hoping somebody can check through my calculations for the determinant of a 4 x 4 matrix.

If anyone noticed any wrong be greatly appreciate if they could correct it saying so.

Thanks a bunch!

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- April 2nd 2008, 06:17 AMmathsTodayDeterminants (do you notice any thing wrong??)
Hi guys,

hoping somebody can check through my calculations for the determinant of a 4 x 4 matrix.

If anyone noticed any wrong be greatly appreciate if they could correct it saying so.

Thanks a bunch! - April 2nd 2008, 08:45 AMtopsquark
- April 2nd 2008, 08:50 AMOpalg
This is where it all starts to go haywire. In the first term, , the 4 should be –4 (because it's the second element in its row, and the +/– signs should alternate as you go along the row). The next two terms should

*both*be multiplied by –3, so that row of the calculation should read .

Similarly, the whole of the last row of the calculation should have the factor of –5, so it should read

Reading further on, I see that two of those errors get corrected in the next line of the calculation. The parentheses are inserted as they should be, and it's only the sign of the 4 that's still wrong:

So the correct answer should be**–**16 – 60**+**80 = 4.

Final comment: this is a terrible method for evaluating a determinant. It's far easier and quicker to use elementary row and column operations (even easier to use a calculator with a determinant facility, but maybe that would be cheating).