## gjhfdfg 2 years ago Gaussian elimination method help?

1. gjhfdfg

I have absolutely know idea how to solve this problem using it, 3x - 2y + 2z - w = 2 4x + y + z + 6w = 8 -3x + 2y - 2z + w = 5 5x + 3z - 2w = 1 Wants me to find the solution

2. gjhfdfg

I mean no instead of know. *face palm*

3. tyteen4a03

The matrix version or the simple "moving variables around" version?

4. gjhfdfg

I believe its the 'simple' moving variables around version

5. tyteen4a03

I just threw this into Wolfram|Alpha, and it didn't give me any value results. Do you need value results?

6. gjhfdfg

Nope, it says find the solution or state that none exists./ So I guess there isnt a solution

7. tyteen4a03

Oh, then I'll show you why there isn't one then. When doing the simple version of Gaussian elimination, always look for "bare" variables first (variables that has a coefficient of 1, otherwise known as "that variable with no numbers"). In this case: 3x - 2y + 2z - w = 2 (1) 4x + y + z + 6w = 8 (2) -3x + 2y - 2z + w = 5 (3) 5x + 3z - 2w = 1 (4) In this case, we notice that in Equation 1 and 3, both w are bare (although there's a minus sign before the w in Eq. 1). Shift w around in Eq. 1 to make it positive again. Now change the subject: 3x - 2y + 2z - w = 2 becomes w = 3x - 2y + 2z - 2 and -3x + 2y - 2z + w = 5 becomes w = 5 + 3x - 2y + 2z. Now that w is (sort of) found, hook them together: 3x - 2y + 2z - 2 = 5 + 3x - 2y + 2z. You see that after simplifying you're left with -2 = 5, which is obviously impossible. Therefore, there is no solution since two of the so-called "related equations" contradict each other.

8. gjhfdfg

Got it, thank you.!

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