Solving Systems of Linear Equations Using Elimination Method

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A Kid Called Matthew

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Sep 19, 2011
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Equation 1. { 4x + 3y = -19
Equation 2. { 5x + 15 = -2y

Now I have a question.

In Equation 2, how come I can't add +2y to both sides to put the equation in standard form such as: 5x +2y = 15?

In order to put it in standard form, I would have to subtract 15 on both sides to put it in standard form as: 5x -2y = -15? How come this is correct and the other way is not?

Re-Written and Solved. Am I Right or Wrong? If wrong, where did I mess up?

2 * {4x +3y = -19
3 * {5x -2y = -15

{8x +6y = -38
{15x -6y = -45

23x = -83

23x/23 = -83/23

x = -83/23.... (this doesn't seem correct!)

I don't even want to go further because I feel this is wrong, that number does not look right! Where did I go wrong? This problem was on a quiz that I got wrong. Please help, much appreciated!

How would I solve this system?
 
A Kid Called Matthew said:
Equation 2.

5x + 15 = -2y

In Equation 2, how come I can't add +2y to both sides to [begin putting] the equation in standard form such as: 5x +2y = 15?

You can. Did somebody tell you otherwise?

Adding 2y to both sides above gives 5x + 2y + 15 = 0.


In order to [continue putting] it in standard form, I would [also] have to subtract 15 on both sides to put it in standard form as: 5x -2y = -15?

Yes, but the result above should have 2y instead of -2y
Click to expand...
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Oh wow! Simple mistake on my part!!!

Thanks to those of you who responded!!!

I understand where I went wrong and WILL NEVER have that problem again!


Thanks to you people, I will get a better grade in my class!
 
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