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Math Help - Finding intersections by adding 2 equations

  1. #1
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    Pshh.
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    Exclamation 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
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  2. #2
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    Scotland
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    Quote Originally Posted by TaylorTeamEdward324 View Post
    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
    If you add two equations, you are their left hand sides together, and their right hand sides together.

    So you'd get:

     x-y + (x+y) = -1+9

     x-y+x+y = 8

     2x = 8

     x = 4

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

     x + y = 9

    4+y = 9

     y = 9-4

     y = 5
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  3. #3
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    Pshh.
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    Question Can you break it down?

    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!!!
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