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anonymous

  • 5 years ago

I need some help solving these problems through elimination. 1) 4x+3y=-1 2x+5y=3 2) 12x-5y=9 3x-8y=-18

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  1. amistre64
    • 5 years ago
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    Is that the intersection of 4 lines? or 2 seperate questions?

  2. anonymous
    • 5 years ago
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    2 seperate questions. If yiu can guide me through the first, maybe I can get the second?

  3. amistre64
    • 5 years ago
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    elimination just means that we modify one equation thru multiplication in order to find a value that can cancel out a variable in the other equation.

  4. amistre64
    • 5 years ago
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    4x+3y=-1 2x+5y=3 <- we can multiply this by -2 to get: -4x should we?

  5. anonymous
    • 5 years ago
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    Ok..

  6. amistre64
    • 5 years ago
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    4x+3y=-1 (2x+5y=3) (-2) 4x +3y =-1 -4x-10y =-6 <-- now we add them together -------------

  7. anonymous
    • 5 years ago
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    So would y be -1

  8. amistre64
    • 5 years ago
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    4x +3y =-1 -4x-10y =-6 ------------ 0 -7y = -7 <-- now we solve for y y = 1 is correct

  9. anonymous
    • 5 years ago
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    not -1. 1?

  10. anonymous
    • 5 years ago
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    ok. got it

  11. amistre64
    • 5 years ago
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    Since y = 1, we can use that to find "x" in the equations...

  12. anonymous
    • 5 years ago
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    Do I just plug the y into one of the equations? or both?

  13. amistre64
    • 5 years ago
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    either one is fine; they both meet at a specific point if they are not parallel lines; and that point has y=1 in common; so use it in any of them to find the common x value

  14. anonymous
    • 5 years ago
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    Ok, so if I plug it into the first equation I got x=1 is rhat right?

  15. anonymous
    • 5 years ago
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    -1

  16. amistre64
    • 5 years ago
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    -1 is good to me :) this is a generic setup so dont be fooled by the position of the solution in my graph.....

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  17. anonymous
    • 5 years ago
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    Oh... thanks, but thankfully my teacher isnt making us graph :)

  18. amistre64
    • 5 years ago
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    You see where the lines cross they have x and y in common right?

  19. anonymous
    • 5 years ago
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    Yes, I do see that.

  20. amistre64
    • 5 years ago
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    the solution to a set of equations is "where the lines have X and Y in common". Or at a single point.

  21. anonymous
    • 5 years ago
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    Thanks for your help. I want to see if I can get the answer to the second one on my own. If I need help will you be around for a few?

  22. amistre64
    • 5 years ago
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    i should be... :)

  23. anonymous
    • 5 years ago
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    Which one should I try to cancel out? Does it matter?

  24. amistre64
    • 5 years ago
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    doesnt matter; pick one and run with it :)

  25. anonymous
    • 5 years ago
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    YAy... I think I got it (3,3) Can you help me with this one or tell me if I'm right. This one is using subsitution. 6x-y=5 y=11x I got x=-5 y=-55 I dont think its right?

  26. amistre64
    • 5 years ago
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    6x - 11x = 5 -5x = 5 x = -1

  27. amistre64
    • 5 years ago
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    since y = "11x" we substitute that value into the other equation: 6x -y = 5 6x - (11x) = 5 ...and solve

  28. anonymous
    • 5 years ago
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    Thank you. I see where I went wrong.

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