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Original Question

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I have to find a value for x. My intial Idea was to let each of the lines equal to 0. Is this the right approach? I have worked down through it based on this but have hit the following sticking point.

First attempt

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    Value for $x$ such that...? – 2017-02-26
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    Sorry Rodrigo dont quite follow what you mean. – 2017-02-26
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    It now says some matrix is zero... – 2017-02-26
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    Am I approaching the question the right way? – 2017-02-26
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    Is the left side of your equation supposed to be *the determinant* of the matrix? If so, do you know how to calculate the determinant of a $3\times3$ matrix? – 2017-02-26
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    Please give more context. Obviously this is not a zero matrix. If the question is about the determinant; that's easy. If the question is about the rank then this is nonsense. – 2017-02-26
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    Ill just add the full question. One minute – 2017-02-26
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    added the original question its at the top. – 2017-02-26
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    Hi Gerry, Now the left side wasnt intended to be determinant of the matrix. Yes I know how to calculate the determinant of a 3x3 matrix should I be doing something that involves that? – 2017-02-26

1 Answers 1

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So got this cleared up in the end. The question should be asking giving the determinant of the matrix given is equal to zero. Find x.

The wrong brackets are used. Should have been straight lines. Thanks to everyone for your input.

Answer I got

Matrix

matrix of minors

7[(3*0) - (-1*x)] -1[(-2*0) - (-1*-1)] + 4[(-2*x) - (3*-1)]

7x -1 -8x + 12

-x + 11 = determinant

∴ -x + 11 = 0
x = -11

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    Much as I expected. So you can do the problem now? – 2017-02-27
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    Yes, I finished the problem. Thnaks for the help! – 2017-03-05
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    Good. Then let me encourage you to write up and post an answer here. – 2017-03-05