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Linear equation

  1. Feb 28, 2010 #1
    Have I got this linear equation right?

    8y - 31 = 13 - 3y

    My answer is y = 8.8
     
  2. jcsd
  3. Feb 28, 2010 #2
    Plug the value you got into the equation and check to see.
     
  4. Feb 28, 2010 #3

    Mark44

    Staff: Mentor

    Your answer is incorrect. Show us how you got your solution and we can steer you in the right direction.
     
  5. Mar 1, 2010 #4

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    Gringo123, I suspect you subtracted 3y from both sides when you should have added it.

    But whenever you ask someone to check your answer, you should always show how you got it.
     
  6. Mar 1, 2010 #5
    Hi Mark. Thanks for helping me out... again!

    1st I added 31 to both sides which left me with:
    8y = 44 + 3y
    From this I could see that 44 = 5y (5y + 3y = 8y)
    44 / 5 = 8.8
     
  7. Mar 1, 2010 #6
    It should be "-" not "+".
    Why did you change this sign?
     
  8. Mar 1, 2010 #7
    Once again I've confused everyone with a typo. The original problem is:
    8y - 31 = 13 - 3y
    I added 31 to both sides:
    8y = 44 - 3y
    Then I add 3y to both sides:
    11y = 44
    and I get the right answer, y = 4
    Iy was a silly little error on my part. Thanks everyone.
     
  9. Mar 1, 2010 #8

    Mentallic

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    Homework Helper

    It's easier to check for yourself if you have the correct answer or not.

    Since you at first found y=8.8, this means if you plug that value in for y in the equation 8y-31=13-3y then you should find that the left-hand side equals the right-hand side. But this isn't true, which means you've made a mistake somewhere. Plugging in y=4 however will make both sides equal, which means you have found the correct value.

    This can be for your quadratics as well.
     
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