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January 31, 2015

January 31, 2015

Posted by **Mathew** on Thursday, January 13, 2011 at 8:55pm.

3x +5y = 3

How come I have to multiply by 5 to make the y variables cancel, like what does that mean? I dont get how ur supposed to multiply like where and how? Im really stuck right now, please help:(

- Necessary Math HELp -
**helper**, Thursday, January 13, 2011 at 9:21pm2x + y = -5

3x +5y = 3

to solve 2 equations simultaneously (at the same time), by elimination, the object is to get rid of one variable.

adding a negative to a positive equals zero, for example, 5y + -5y = 0.

So, to get rid of y in the above 1st equation, since the first equation has just "y" and the second equation has "5y", you multiply the first equation by -5 to get "-5y" so that the -5y added to 5y = 0,

Multiply the whole equation by -5

-5 (2x + y = -5) = -10x - 5y = 25

Now add the two equations together

-10x - 5y = 25

3x + 5y = 3

-7x + 0 = 28

-7x = 28

x = -4

substitute x = -4 in either equation and solve for your y value

do you understand this?

- Necessary Math HELp -
**Mathew**, Thursday, January 13, 2011 at 9:28pmWow helper:D

Thanks a lot buddy, I really appreciate all the time you put to help me with my question. Yeah thanks to your explanation I get it, thanks a lot:)

So here's how I substitute right?

2x+y = -5

2(-4)+y = -5

-8 +y = -5

Then I add 8 to both sides and get:

y = -3

Therefore the solution would be:

(-4,3)

- Necessary Math HELp -
**helper**, Thursday, January 13, 2011 at 9:32pmcorrect, the answer is (-4, 3)

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