Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Find a and b

  1. Nov 3, 2012 #1

    utkarshakash

    User Avatar
    Gold Member

    1. The problem statement, all variables and given/known data
    If [itex]x_1,x_2[/itex] are the roots of [itex]x^2-3x+a=0[/itex] and [itex]x_3,x_4[/itex] are the roots of the equation [itex]x^2-12x+b=0[/itex] and [itex]x_1,x_2,x_3,x_4[/itex] are in increasing G.P., find a and b

    2. Relevant equations

    3. The attempt at a solution
    [itex]x_1+x_2=3 \\
    x_1x_2=a \\
    x_3+x_4=12 \\
    x_3x_4=b[/itex]

    But these are not sufficient to find a and b. Also what is meant by an increasing G.P.?
     
  2. jcsd
  3. Nov 3, 2012 #2

    SammyS

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    G.P. = Geometric Progression

    http://en.wikipedia.org/wiki/Geometric_progression
     
  4. Nov 3, 2012 #3
    It means that the common ratio of the GP is greater than 1.
     
  5. Nov 4, 2012 #4

    utkarshakash

    User Avatar
    Gold Member

    This means that [itex]x_1<x_2<x_3<x_4[/itex]
    But what is the use of this in my question?
     
  6. Nov 4, 2012 #5

    Mentallic

    User Avatar
    Homework Helper

    Ignoring that detail for the moment, simply try answer the question and then you'll see.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook