+0  
 
0
397
6
avatar+266 

 

 

?

 Jan 15, 2016

Best Answer 

 #6
avatar+96080 
+10

Here's 10, Paypay.......this one is more complicated.......there are at least two other ways to do this, but the one presented is more "mechanical"

 

Here's the procedure

 

 

Let's find the determinant of your matrix, first

 

1  0   1    1   0

1  1  -4    1   1

0  1  -4    0   1

 

Multiply down the diagonals, sum the products

 

[(1*1 *-4   + 0  + 1] =   [-4 + 1]  = -3

 

Multiply up the diagonals, sum the products

 

[0 + 1*-4*1 + 0]  =  -4

 

Subtract the second thing from the first   -3 - (-4)   = 1

 

That's nice.......we don't even need to worry about the det, now   !!!!

 

Now......we take each of the determinants specified in the "formula" and put the results in the proper places

 

Note.....since the given answers all have the same top row.......we can ignore this.....let's fill in the rest, staring with the second row

 

So.......filling in and evaluating we have

 

element 21  = a23  a21   =  [-4*0] - [1 *-4]  = 4

                      a33   a31

 

Npw.....we can eliminate F  and J as answers  since element 21  in both = -4

 

The next elemnent, 22, is the same in  G  and H....so let's calculate  element 23

 

element 23  = a13   a11   = [1*1] - [1*-4]  = 5

                      a23    a21

 

Then.....H looks to be correct.....!!!

 

I have verified this using this app :http://matrix.reshish.com/inverCalculation.php

 

In general....another method kown as "Gaussian Elimination" requires WAY less memorization, but it's easy to make mistskes amd you have to deal with some nasty fractions, at  times....!!!

 

 

cool cool cool

 Jan 15, 2016
 #1
avatar+4080 
+5

Sorry to say this, but I'm tired of matrix... I dunno what that is, but you had like three of them last night.......

 Jan 15, 2016
 #2
avatar+8613 
0

LOL! Rightt!

 Jan 15, 2016
 #3
avatar+266 
0

then mind your own d**n business. problem solved!

 Jan 15, 2016
 #4
avatar+96080 
+5

Here's  9

 

The inverse of a 2 x 2 matrix in this form        a   b       is given by :

                                                                        c   d

 

[1 / det of the matrix]     x    [  d   - b

                                             -c     a  ]

 

The determinant of the given matrix = [2 *3] - [-5 * 5]   = 6 + 25   = 31

 

So  we have

 

[1/ 31]     x    [3     - 5      =   [ 3/31     -5/31

                      5       2 ]           5/31      2/31 ]

 

(B)  is correct

 

 

cool cool cool

 Jan 15, 2016
 #5
avatar+8613 
0

D**n!! >_>

 Jan 15, 2016
 #6
avatar+96080 
+10
Best Answer

Here's 10, Paypay.......this one is more complicated.......there are at least two other ways to do this, but the one presented is more "mechanical"

 

Here's the procedure

 

 

Let's find the determinant of your matrix, first

 

1  0   1    1   0

1  1  -4    1   1

0  1  -4    0   1

 

Multiply down the diagonals, sum the products

 

[(1*1 *-4   + 0  + 1] =   [-4 + 1]  = -3

 

Multiply up the diagonals, sum the products

 

[0 + 1*-4*1 + 0]  =  -4

 

Subtract the second thing from the first   -3 - (-4)   = 1

 

That's nice.......we don't even need to worry about the det, now   !!!!

 

Now......we take each of the determinants specified in the "formula" and put the results in the proper places

 

Note.....since the given answers all have the same top row.......we can ignore this.....let's fill in the rest, staring with the second row

 

So.......filling in and evaluating we have

 

element 21  = a23  a21   =  [-4*0] - [1 *-4]  = 4

                      a33   a31

 

Npw.....we can eliminate F  and J as answers  since element 21  in both = -4

 

The next elemnent, 22, is the same in  G  and H....so let's calculate  element 23

 

element 23  = a13   a11   = [1*1] - [1*-4]  = 5

                      a23    a21

 

Then.....H looks to be correct.....!!!

 

I have verified this using this app :http://matrix.reshish.com/inverCalculation.php

 

In general....another method kown as "Gaussian Elimination" requires WAY less memorization, but it's easy to make mistskes amd you have to deal with some nasty fractions, at  times....!!!

 

 

cool cool cool

CPhill Jan 15, 2016

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