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Homework Help: Basic algebra question

  1. Jul 17, 2006 #1
    basic algebra question plz help :(

    when combining the two equations

    Vb-0.5FAC = 10
    Hb -0.866FAC = -2

    It brings the answer 1.732Vb - Hb = 19.32

    can someone plx explain to me how this answer came about
  2. jcsd
  3. Jul 17, 2006 #2


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    Gold Member

    You have Vb, Hb, and FAC as variables with only two equations?

    Of course you're not going to solve it. Do these variable stand for something significant? Perhaps there is a third equation that you're missing
  4. Jul 17, 2006 #3
    They substituted FAC from the first equation into the second one. Now try to find this answer yourself.
  5. Jul 17, 2006 #4
    the answer i got myself was
    1.732Vb - Hb = 12

    i got no idea how they got 19.32
  6. Jul 17, 2006 #5
    did you came up with FAC = -20 + 2Vb ?
  7. Jul 17, 2006 #6
    yes that is correct

    there is actually a third equation that when combined with the first two equations gives all the answers

    the third equation is
    2Vb - 3Hb = -26

    the final answers are

    Vb = 26.2
    Hb = 26.1
    FAC = 32.4

    The problem i have is that i dont understand how the first two equations combined together gave the answer of 1.732Vb - Hb = 19.32

    if you could write down the step by step procedure on how this answer came about it would be greatly appreciated.
  8. Jul 17, 2006 #7
    i won't write down all my steps because it's not allowed. Here is how you get to the equation that leads to 1,732Vb - Hb = 19,32:

    From equation 1 it follows that:

    [tex] FAC = \frac {(10-Vb)} {-0,5} \ = -2 (10-Vb) = -20 + 2Vb [/tex]

    This can be put in the second equation:

    [tex]Hb -0.866(-20 + 2Vb) = -2 [/tex]

    This will deliver your asked formula when properly worked out.
    Last edited: Jul 17, 2006
  9. Jul 17, 2006 #8
    thank you so much

    i swear to god if i had a credit card i would pay you 5 dollers
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