Math Is Fun Forum

Douglasm

Member

Registered: 2009-12-25

Posts: 15

Linear Systems

I having some trouble with this question. It's a question from IME (Instituto Militar de Engenharia - Engeneering Military Institute):

Determine the value of

that satisfies the system of linear equations:

(I coundn't figure out how to use the array comand here...)

I hope someone can help me...=)

The answer:

Last edited by Douglasm (2010-01-06 09:53:36)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Linear Systems

Hi Douglasm;

Were you expected to do this by hand?

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Ricky

Moderator

Registered: 2005-12-04

Posts: 3,791

Re: Linear Systems

Are you having problems using row reduction?  Or do you not know it?

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"In the real world, this would be a problem.  But in mathematics, we can just define a place where this problem doesn't exist.  So we'll go ahead and do that now..."

Douglasm

Member

Registered: 2009-12-25

Posts: 15

Re: Linear Systems

Actually I've reduced it using the Chió Rule. I was trying to find the

using the Cramer's method (the most logical way of solving it). But I coudn't find the right answer. This question is from the admission test of IME, so I have to solve it by hand. I'm having a hard time here...

Ricky

Moderator

Registered: 2005-12-04

Posts: 3,791

Re: Linear Systems

Cramer's method

Do you perhaps mean Cramer's rule?  It is typically easier to solve the system using row reduction than finding the inverse matrix.

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"In the real world, this would be a problem.  But in mathematics, we can just define a place where this problem doesn't exist.  So we'll go ahead and do that now..."

Douglasm

Member

Registered: 2009-12-25

Posts: 15

Re: Linear Systems

That's it, I got confused with the names in English (I'm brazilian). I will try to solve it again, maybe I'm doing something wrong in the reduction...

Douglasm

Member

Registered: 2009-12-25

Posts: 15

Re: Linear Systems

I was doing the reduction wrong! I found the right answer now. I just used the gaussian elimination, and it was easy to solve. Thank you for your assistance.