Solving systems of two linear equatons by elimination

[bnorth22]

My text book says STEP1: First get the coeffcients on one of the variables
to be addative inverse.

Then they give the following example:
equation1 5x+2y=-5
equation2 -2x-4y=-14


equation1 2(5x+2y)=2(-5)
equation2 -2x-4y=-14

Then it explains: In loking at this system, we can make the coeffcient y to be the addative inverse by multiplying equation (1) by 2.


This is what I don't understand. Where do they get the 2 from. I think I would be ok if some one could just explain what is ment by making the coefficient on one of the variables to be the addative inverse. The addative inverse of what? Please some one help me.



Thanks


Brittany

 

[jonboy]

Hello, bnorht!

I have to admit, that big word additive inverse seems very perplexing. All it means is taking a number that will cancle out another number by addition. Like: 2y + (- 2y) , 3y + (- 3y) , etc.

Changing 5x+2y=-5 => 2(5x+2y)=2(-5) => 10 + 4y = -10

Was done so you could add: 10x + 4y = - 10 & -2x-4y=-14 (the 4y is the additive inverse of -4y) and get a one variable equation, 8x = -28.

 

[bnorth22]

Thank you soooooo much. Now I can get my work done for class tomorow. For this I say I love you you are my savior

 

[jonboy]

Thank you soooooo much. Now I can get my work done for class tomorow. For this I say I love you you are my savior

Haha , You welcome, glad my explanation worked.

 

[skeeter]

Was done so you could add: 10x + 4y = - 10 & -2x-4y=-14 (the 4y is the additive inverse of -4y) and get a one variable equation, 8x = -28.

... 8x = -24