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Solve the simultaneous equations:

70-T=7a

T-40=4a

By multiplying both sides of the equations by a factor and shifting the terms I transformed them into the following form:

-28a-4T=-280

-28a+7T=+280

Further simplification results in a single equation as follows:

-11T=-560

So, T is a recurring number, which I know cannot be correct, so where am I going wrong?

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  • $\begingroup$ So this will get removed because it has nothing to do with the software Mathematica, it's just a math question. That being said, you did everything right up to the end, and you just need to take it a step further to get that T=560/11. Then substitute this into either of the first two equations to solve for a. $\endgroup$
    – Jason B.
    Sep 2, 2015 at 9:46
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    $\begingroup$ I'm voting to close this question as off-topic because it is about mathematics and not about the software system Mathematica. $\endgroup$
    – Michael E2
    Sep 2, 2015 at 10:00
  • $\begingroup$ could we get this question moved to the mathematics site? $\endgroup$ Sep 2, 2015 at 10:30
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    $\begingroup$ @DarthVader, actually if you'll check my comment and Inari's answer below, there isn't any need to move this question. You have your answer $\endgroup$
    – Jason B.
    Sep 2, 2015 at 12:10

1 Answer 1

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I am a bit startled as to your question. This is a system of linear equations, two equations, two variables, thus if there is a solution, there is one unique one. This you have found, as T = 560/11 -> a = 30/11. This is all, is it not?

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  • $\begingroup$ I think, upon 2nd thought, that the solution does not need to be unique, but well ... in this case it is :D It'd depend on wheter the determinant of the matrix is unequal zero in general ... but that's maybe thinking too much for this simple problem. $\endgroup$
    – Inari
    Sep 2, 2015 at 12:57

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