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ValentinaT

  • 2 years ago

Solving systems by substitution and elimination?

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  1. ValentinaT
    • 2 years ago
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    \[y = \frac{ 1 }{ 2 }x - 6\] 2x + 6y = 19

  2. ValentinaT
    • 2 years ago
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    I know that answer is (11, -1/2) but I don't know how to solve it.

  3. cgreenwade2000
    • 2 years ago
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    So, you know what y equals. If you see y in another equation can't you just plug it in?

  4. ValentinaT
    • 2 years ago
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    What I meant is that, someone told me the answer, but not how they got it. Could you explain to me how they would have got (11, -1/2) as the answer?

  5. cgreenwade2000
    • 2 years ago
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    I will ask you a series of questions to help you solve this. Question 1: what does y equal?

  6. ValentinaT
    • 2 years ago
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    -1/2

  7. cgreenwade2000
    • 2 years ago
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    Y does not equal -1/2 Read the first equation out loud and listen to what y is equal to.

  8. ValentinaT
    • 2 years ago
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    1/2 - 6

  9. cgreenwade2000
    • 2 years ago
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    If x = 25r + 25b Then x is equal twenty-five r plus twenty-five b.

  10. ValentinaT
    • 2 years ago
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    Okay.

  11. cgreenwade2000
    • 2 years ago
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    Y = 1/2X - 6 There is no other answer. By writing y=1/2x-6 We say Y is equal to one half of x minus 6. There is nothing else that is the answer.

  12. cgreenwade2000
    • 2 years ago
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    Question 2: If x = 5, what is y , if: x + 10 = y

  13. ValentinaT
    • 2 years ago
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    x plus ten.

  14. cgreenwade2000
    • 2 years ago
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    This is the substitution part, if you know that x is 5..... What is y?

  15. cgreenwade2000
    • 2 years ago
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    Y would then be x+10=y 5+10=y 15=y

  16. ValentinaT
    • 2 years ago
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    Okay.

  17. cgreenwade2000
    • 2 years ago
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    Now that's just a basic use of substitution. Let's go back to your problem(s) You know what y is equal to y=1/2x-6 So then you look at the other equation 2x + 6y = 19 and say Well if i know what y is, I can replace it with the y there. So 2x + 6y = 19 turns into 2x + 6(1/2x - 6) = 19

  18. ValentinaT
    • 2 years ago
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    Okay.

  19. cgreenwade2000
    • 2 years ago
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    So there's the way to solve for x. Once you get a numerical answer for x, you can solve for y.

  20. ValentinaT
    • 2 years ago
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    Okay, so what do you do afterwards?

  21. cgreenwade2000
    • 2 years ago
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    Did you solve for x?

  22. ValentinaT
    • 2 years ago
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    Well, what I meant was do i combine 2x and 1/2x?

  23. cgreenwade2000
    • 2 years ago
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    You need to distribute the 6 since it was 6y and then you can proceed with solving for x from there.

  24. ValentinaT
    • 2 years ago
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    5x - 36 = 19 5x = 55 x = 11 Replace x in one of the equations. y = 1/2(11) - 6 y = 5.5 - 6 y = -1/2

  25. cgreenwade2000
    • 2 years ago
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    And you have just solved by substitution.

  26. ValentinaT
    • 2 years ago
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    How do you go from 2x + 6(1/2x - 6) = 19 to 5x - 36 = 19?

  27. cgreenwade2000
    • 2 years ago
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    6 times 1/2x equals 3x and -6 times 6 equals -36 You may need to go back and review some algebra. It would help tremendously and I do not see another way for you to continue in mathematics without it.

  28. cgreenwade2000
    • 2 years ago
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    I am going to link you to some pages. Please study them and use them and I suggest understanding these concepts before continuing your homeworkl.

  29. ValentinaT
    • 2 years ago
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    I've done the other problems myself, its just that i didn't understand this one.

  30. ValentinaT
    • 2 years ago
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    *I

  31. cgreenwade2000
    • 2 years ago
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    Distribution property is one of the earliest rules learned in algebra. If you can get from 2x + 6(1/2x-6) = 19 to 5x-36=19 well then there may be some necessary review:

  32. cgreenwade2000
    • 2 years ago
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    http://www.worksheetworks.com/math/pre-algebra/equations-like-terms-distributive.html

  33. ValentinaT
    • 2 years ago
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    Thank you.

  34. ValentinaT
    • 2 years ago
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    What do you want?

  35. ValentinaT
    • 2 years ago
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    I blocked you?

  36. ValentinaT
    • 2 years ago
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    It doesn't say I did.

  37. ValentinaT
    • 2 years ago
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    It doesn't say I blocked you. I have to go.

  38. mustry
    • 2 years ago
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    where?

  39. mustry
    • 2 years ago
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    Valentina?

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