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anonymous

  • 5 years ago

y=4x x+y=5

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  1. anonymous
    • 5 years ago
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    hello

  2. anonymous
    • 5 years ago
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    this is a classic "substituion" problem

  3. anonymous
    • 5 years ago
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    the idea is that you want to take the value of a variable from one equation, and "substitute" that into the other

  4. anonymous
    • 5 years ago
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    since you have two unknowns, you need two equations - which you have

  5. anonymous
    • 5 years ago
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    so let's take y=4x and substitute it into the second equation

  6. anonymous
    • 5 years ago
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    so x+y = 5 becomes x + (4x) = 5 (I just replaced y in the second equation with what the first equation asserted y to be)

  7. anonymous
    • 5 years ago
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    that is called subsitution

  8. anonymous
    • 5 years ago
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    so x+4x =5, 5x=5, and now divide both sides by 5 for the answer

  9. anonymous
    • 5 years ago
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    so x = 1

  10. anonymous
    • 5 years ago
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    now that you have x, you can substitute that back into either equation to get the value of y

  11. anonymous
    • 5 years ago
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    so x+y = 5, and I know that x=1. so 1+y=5, 1-1+y = 5-1, y=4 (subtract 1 from both sides)

  12. anonymous
    • 5 years ago
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    i got up to x=1 then got confused on Y

  13. anonymous
    • 5 years ago
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    ok great

  14. anonymous
    • 5 years ago
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    well, think of x=1 as just another piece of information you now have, along with the original equations

  15. anonymous
    • 5 years ago
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    so if x+y = 5 , and I already know x=1, then I can substitute the value of x in that first equation with what I know to be true

  16. anonymous
    • 5 years ago
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    so 1 + y = 5

  17. anonymous
    • 5 years ago
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    and then y=4

  18. anonymous
    • 5 years ago
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    you can always check your work at the end of these problems too

  19. anonymous
    • 5 years ago
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    plug in 4x for y x+4x=5 5x=5 5 divided by 5 = 1

  20. anonymous
    • 5 years ago
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    so our guess is that x = 1, and y = 4

  21. anonymous
    • 5 years ago
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    if you stick those back into the original equations, do they hold true?

  22. anonymous
    • 5 years ago
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    yes

  23. anonymous
    • 5 years ago
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    if they do, then you know you did it right

  24. anonymous
    • 5 years ago
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    ok. got it. thank u

  25. anonymous
    • 5 years ago
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    np!

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