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Homework Help: Algebra again

  1. Sep 29, 2005 #1

    DB

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    can some 1 give me a hand with this? thanks
    [tex]\frac{150}{v+20}+\frac{150}{v-5}=3.5[/tex]
     
  2. jcsd
  3. Sep 29, 2005 #2
    1. make the denominator the same.
    2. cross multiply the equation to get rid of the fraction form.
    3. solve the quadratic equation.
     
  4. Sep 29, 2005 #3

    DB

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    i get the -65 n 80 which i think is right so thanks leong
     
  5. Sep 29, 2005 #4
    check your answer !
     
  6. Sep 29, 2005 #5

    DB

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    80 works, -65 doesnt
     
  7. Sep 29, 2005 #6

    DB

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    it came down to:
    [tex]3.5v^2+52.5v-650[/tex]
     
  8. Sep 30, 2005 #7

    VietDao29

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    Homework Helper

    Uhmmm, I think you should check your calculation again.
    Here we go:
    [tex]\frac{150}{v + 20} + \frac{150}{v - 5} = 3.5[/tex]
    Multiply both sides by (v + 20) (v - 5)
    [tex]\Leftrightarrow (v + 20)(v - 5)\left(\frac{150}{v + 20} + \frac{150}{v - 5}\right) = 3.5(v + 20)(v - 5)[/tex]
    [tex]\Leftrightarrow 150(v - 5) + 150(v + 20) = 3.5(v ^ 2 + 15v - 100)[/tex]
    [tex]\Leftrightarrow 300v + 2250 = 3.5v ^ 2 + 52.5v - 350[/tex]
    [tex]\Leftrightarrow ...[/tex]
    Can you go from here?
    By the way, it does not come down to 3.5v2 + 52.5v - 650 = 0.
    Viet Dao,
     
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