Finding determinant 4*4

"Solve" what?? Your link gives M equal to a specific matrix. What are you asked to do with it?
 
Lazar said:
I need to find m so that detM = 0
Click to expand...

What method have you been taught for calculating the determinant of a 3x3 matrix?

You can extend the same reasoning to a 4x4 matrix.

Please show us what you have already tried.

There are two solutions for m.

:)
 
Quaid said:
What method have you been taught for calculating the determinant of a 3x3 matrix?

You can extend the same reasoning to a 4x4 matrix.

Please show us what you have already tried.

There are two solutions for m.

:)
Click to expand...


I know with rule of Saurrus ot to make it , all zeroes above , or under the main diagonal and just to multiple all elements on tha main diagonal , but cant make all zeores.
i am trying to find different route than Laplace , sorry for not making it with work was really tired last night.
 
Your solution matches mine. Good job. :D


Lazar said:
I know with rule of Saurrus...

trying to find different route than Laplace...
Click to expand...

You're ahead of me; I never learned either of those methods.

I did it the old-fashioned (i.e., tedious) way.

\(\displaystyle A \;=\;\begin{bmatrix}A&B&C&D\\E&F&G&H\\I&J&K&L\\M&N&O&P\end{bmatrix}\)

Det(A) = AFKP - AFLO - AJGP + AJHO + ANGL - ANHK - EBKP + EBLO + EJCP - EJDO - ENCL + ENDK + IBGP - IBHO - IFCP + IFDO + INCH - INDG - MBGL + MBHK + MFCL - MFDK - MJCH + MJDG

It's easy to see -- by inspection -- that this sum will be zero when all of the symbols equal 1.

To get the other solution, I had to substitute m for A, F, K, P and substitute 1 for all the rest. That gave me a 4th-degree polynomial in m.

Hope your method was easier!
 
I ll post the detailed explanitaon later after 13th July i have a big exam than so i am just studying xD
 
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