4x4 determinant

soccerball3211

Junior Member
Joined
May 16, 2005
Messages
84
Ok, i know I have to get a row or a column with as many zeros as possible but then what do I do(I chose the first column because there are already two zeros in it)

[1 -3 -5 6]
[0 1 -8 1]
[0 9 2 1]
[5 0 -1 7]
 

soroban

Elite Member
Joined
Jan 28, 2005
Messages
5,588
Hello, soccerball3211!

i know I have to get a row or a column with as many zeros as possible
but then what do I do? . . . you're stuck already?
(I chose the first column because there are already two zeros in it) . . . good!
Code:
[1 -3 -5  6]
[0  1 -8  1]
[0  9  2  1]
[5  0 -1  7]
Amazing ... you're totally unfamiiar with any of the Row Operations?

Take row-4 and subtract 5 times row-1.
. . . That creates a zero at the lower-left.
(And that's the best we can do.)
 

arthur ohlsten

Full Member
Joined
Feb 20, 2005
Messages
854
A determinant is a number IT IS NOT A SQUARE MATRIX
Expand the determinant as 4, 3x3 determinants and evaluate each but change signs

[1 -8 1] [-3 -5 6]
1[9 2 1] -0[] +0[] -5 [ 1 -8 1]
[0 -1 7] [9 2 1]

1( 14 -9+1+504] -5( -432-6-5-24 +45-12)
(510)-5(-434)
510+2170
2680 answer
please check math for errors
Arthur
 

soccerball3211

Junior Member
Joined
May 16, 2005
Messages
84
answer

I got -1660
 

pka

Elite Member
Joined
Jan 29, 2005
Messages
7,954
You are corrct!
 
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