Question

any body to help me on 4*4 matrix

Answer 1

what is the help you want? you post your question.. we will help

Answer 2

how calculate 4by4 matrix

Answer 3

umm yeah ...what happened to the last post you never posted anything

Answer 4

i have posted one on crammer rule

Answer 5

calculate what? the determinant

Answer 6

5 6 7 8
8 0 3 2
4 5 6 7
7 8 9 9

Answer 7

that is the question

Answer 8

easy but a little lenghty

Answer 9

11

http://www.wolframalpha.com/input/?i=determinant+ {{5%2C6%2C7%2C8}%2C{8%2C0%2C3%2C2}%2C{4%2C5%2C6%2C7}%2C{7%2C8%2C9%2C9}}

Transform to upper/lower triangular and product of entries on main diagonal.

Answer 10

Hmm, I'm not a matrix expert but I thought if u upper or lower triangular then det is multiply entries main diagonal, is that wrong?

Answer 11

no thats correct.

Answer 12

See, if u go Wolfram with link above, says det is 11.

If u upper tri http://www.wolframalpha.com/input/?i=upper+triangular+ {{5%2C6%2C7%2C8}%2C{8%2C0%2C3%2C2}%2C{4%2C5%2C6%2C7}%2C{7%2C8%2C9%2C9}}

??

Answer 13

i dont think that command is doing what we think it is. Theres a little description that says that command is just replacing everything below the main diagonal with zeros. Its not doing row operations to get an upper triangular matrix.

Answer 14

Any other way? Apart from doing it by hand.

Answer 15

5 6 7 8
0 0 3 2
0 0 6 7
0 0 0 9
it is triangularized by mathematica, it will result in 0, whats the matter

Answer 16

not really =/ thats why cramer's rule isnt exactly thrilling to use. if you have an nxn martix, you have to calculate n+1 nxn determinants >.< gross gross.

Answer 17

Can u decompose into simple matrices?

Answer 18

yp

Answer 19

yp?

Answer 20

yes i can

Answer 21

Name of algorithm?

Answer 22

i dont remember the name but i can find every thing regarding matrix

Answer 23

So can I, thought u might know...

Answer 24

row and column operations plus expanding is the common method

Answer 25

OK, seems we have

LU Decomp, Gaussian, Singular Value, Eigen Decomp and Jordan Normal Form

Any of these make it easier to calculate determinant.

What I am trying to do is check the 11 given by Wolfram.

Answer 26

Any of these make it easier to calculate determinant?

Answer 27

II will try tooooooo

Answer 28

Here is LU Decomp

http://www.wolframalpha.com/input/?i=Lu+decomposition {{5%2C6%2C7%2C8}%2C{8%2C0%2C3%2C2}%2C{4%2C5%2C6%2C7}%2C{7%2C8%2C9%2C9}}

Answer 29

Jordan

http://www.wolframalpha.com/input/?i=Jordan+Normal+Form {{5%2C6%2C7%2C8}%2C{8%2C0%2C3%2C2}%2C{4%2C5%2C6%2C7}%2C{7%2C8%2C9%2C9}}

Answer 30

Singular Value

http://www.wolframalpha.com/input/?i=Singular+value+decomposition {{5%2C6%2C7%2C8}%2C{8%2C0%2C3%2C2}%2C{4%2C5%2C6%2C7}%2C{7%2C8%2C9%2C9}}

Answer 31

Laplacian by minors seems like useful but I can't get Wolfram to do it...

Answer 32

need to be solve by hand in full length, also if u have matlab try on it

Answer 33

i did, do the following operations
1. C4-C3
2. R1-R3
3. R2+R3
now expand it , its very easy resulting in 11

Answer 34

Ok, so why upper triangular in Wolfram doesn't give?

Answer 35

what is the problem here ? i don't get it




for 4x4 matrix

you have to solve it just like 3x3

Answer 36

You want a good way to calculate the determinant by hand?

Answer 37

Wolfram calculates det correctly with det command = 11

Answer 38

But should be same as multiplying entries on diagonal of upper diagonal matrix and isn't.

Answer 39

I don't want to calculate matrices by hand....yuk!

Answer 40

ok wait let me solve it

Answer 41

Maybe they are taking out a factor or something...

Answer 42

I am getting very bad value ..maybe some kinda row or column thing might work like most of the rows i mean if i subtract R_2 - R_1 then i get -1 thing and same goes with other

Answer 43

Lets perform C_1 -> C_1 - C_2

C_2->C_2 - C_3
C_3->C_3 - C_4

Sorry Column not Rows I got Confused

Answer 44

U are using row operations to get upper triangular, right?

Answer 45

Then I get

-1 -1 -1 8
8 -3 -1 2
-1 -1 -1 7
-1 -1 0 9

Answer 46

Kinda I am just trying to simplify

Answer 47

Or lower..

Answer 48

Got it Lets do R_4->R_4 - R_3

Answer 49

We will get

In the Last Column 0 0 1 9

Answer 50

sorry 0 0 1 2

Answer 51

Now all we have to do is to solve 1 and 2

Answer 52

U can do with R2?

Answer 53

I mean we can now expand R_4

Answer 54

This why I don't like calculations...:-)

Answer 55

Too easy to make mistakes.

Answer 56

I never Liked Matrices and Determinants

Answer 57

I am used to vector representations and orthogonal bases, much easier to understand.

Answer 58

I guess safest thing is not to use upper triangular command in Wolfram..:-)

Answer 59

It's enough I guess no need for calculating ...

Answer 60

Yes, he has answer 11 and ZakaullahUET gave the operations to calculate it by himself.

Answer 61

I will try to find out what Wolfram is doing...:-(

Answer 62

I never tried wolfram for Matrices I will try them Now