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anonymous
 one year ago
Evaluate the determinant of the matrix
[8. 3 2]
[1 3 2]
[ 5 1 1]
anonymous
 one year ago
Evaluate the determinant of the matrix [8. 3 2] [1 3 2] [ 5 1 1]

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UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.1cofactor expansion... that's needed to shrink the matrix down to a 2 x 2

DanJS
 one year ago
Best ResponseYou've already chosen the best response.0do you know a 2 by 2 determinant?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0yes! i just don't know how to find the determinant for a 3x3 matrix

DanJS
 one year ago
Best ResponseYou've already chosen the best response.0Determinant of 2 by 2 matrix = a*d  cd [a b] [c d]

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.1ad  bc for determinant of a 2 x 2 matrix for a 3 x 3 matrix we have to use cofactor expansion.

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0how do i do cofactor expansion?

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.1Cofactor expansion expanding a row ... find the minors and the cofactors of the first row entries ( you can choose second row or third row entries but the sign pattern is different).

DanJS
 one year ago
Best ResponseYou've already chosen the best response.0Cover first column, 8*det of that 2x2 is the first of 3 terms

DanJS
 one year ago
Best ResponseYou've already chosen the best response.0look up determinant of 3 x 3 matrix.. lol this is alot of drawing

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.1the signs for the 3 x 3 matrix is like a checkerboard dw:1438053171537:dw that's why I use the first drawing a lot.

DanJS
 one year ago
Best ResponseYou've already chosen the best response.0yeah i just remember the second is minus

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.1dw:1438053270643:dw

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.1cut row one cut column one cut row one cut column two cut row one cut column three

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.1dw:1438053376916:dw

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.1ok I'm going to clean this up a bit.. but where I circled the row and column... you draw a line to cross them out... you should be left with 4 numbers... that's your 2 x 2 matrix. now you can take the determinant of those matrices...

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.1dw:1438053458361:dw

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.1dw:1438053534643:dw

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.1dw:1438053599579:dw normally we would have a + sign but that negative 2 on the first row third column entry changes that.

UsukiDoll
 one year ago
Best ResponseYou've already chosen the best response.1dw:1438053728550:dw so we should have this equation after we have done cofactor expansion. Now we can take the determinant of the 2 x 2 matrix and combine like terms. The final answer for the determinant of the 3 x 3 matrix should be just a single number
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