Finding intersections by adding 2 equations

For each of the following pairs of equations, find the point of intersection by adding the two equations together. Remember: you might need to change the coeffients and/or signs of the variables before adding.

Help!

x-y = -1
x+y= 9

Quote:

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Originally Posted by TaylorTeamEdward324

For each of the following pairs of equations, find the point of intersection by adding the two equations together. Remember: you might need to change the coeffients and/or signs of the variables before adding.

Help!

x-y = -1
x+y= 9

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If you add two equations, you are their left hand sides together, and their right hand sides together.

So you'd get:









Then just put x = 4 into one of the original equations to get y!

Okay? What I don't understand is how you got the -1 and why you have the x - y (x+y)... I don't understand what the reasoning is behind that. Could you explain that to me?

Thanks so much for helping me... I AM getting the same answer but not really understanding the way I'm getting it.. make sense? LOL

Thanks again!!!