Simultaneous equations

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Adam Preston
Posts: 102
Joined: Sat Mar 19, 2011 10:29 pm UTC

Simultaneous equations

Postby Adam Preston » Wed Nov 30, 2011 2:48 pm UTC

Not sure if they are called Simultaneous equations as my education is mostly in welsh, but I'll give you an example :
Y = 2x -4 1.
Y = 3x - 5 2.

How would I be able to solve these equations? seeing as they're both equal to Y wouldn't I be able to put them both equal to each other then solve that equation?

3x - 5 = 2x -4
x -5 = -4
x = 1
Correct? Seeing as Y is equal to negative 2 in both equations?
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the tree
Posts: 801
Joined: Mon Apr 02, 2007 6:23 pm UTC
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Re: Simultaneous equations

Postby the tree » Wed Nov 30, 2011 2:55 pm UTC

Yeah they're called simultaneous equations. And yes that's gotten you a correct answer. (although it took me a minute to realise that the 1 and 2 and the end of each wasn't part of the equations, typically you'd put those in brackets or something to avoid ambiguity).

Another way you could have done that was by elimination;

eqn2 - eqn1 would give you: 0 = x -1, and you could solve from there.

You could also have taken a graphical approach as shown by wolfram alpha, so that you can 'see' why that's the answer.

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