Question

Calculate the determinants of the following

Answer 1

-4 5 2
-2 3 1
2 4 -2

Answer 2

now i row reduce.
-4 5 2
0 -1 0
2 4 -2
(R2=R1-2R2)

Answer 3

then i take the determinant of :
\[\left[\begin{matrix}-4 & 2 \\ 2 & -2\end{matrix}\right] * -1\]

Answer 4

is this correct?

Answer 5

anyone?

Answer 6

\(\left[\begin{matrix}-4 & 2 \\ 2 & -2\end{matrix}\right] * -(-1)\)

Answer 7

no its
+ - +- ..
- + -+..
...

Answer 8

oops :P
yes., then its correct :)

Answer 9

but, the thing is. the answer is 2. not -4

Answer 10

if you work it out the long hand way, you get 2. but using this way, you dont seem to get the right answer

Answer 11

oh ok i was just checking that...i didn't think you could row reduce like that

Answer 12

i belive you can http://www.youtube.com/watch?v=Lu50tv7Gmoc

Answer 13

yes, when you multiply the R2 by 2, you should have to divide it also...outside the determinant

Answer 14

really, i'll look that one up.

Answer 15

ok, listen here http://youtu.be/Lu50tv7Gmoc?t=1m40s

Answer 16

right, row reducing is used for solving when there are 2 matrices and an equal sign

wolfram uses the long way... -4*det -5*det +2*det

Answer 17

he says, row operations have no effect

Answer 18

infact, you multiplied R2 by (-2)
you'll need to divide it by -2
-4/-2 = 2

Answer 19

i dont get that, look at the video. he says when your doing row operations, this doesn't effect the determinant.

Answer 20

this is the basic, you cannot just multiply a row with any constant ...you'll need to divide it too...