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Functions and quadratic equations

  1. Nov 26, 2003 #1
    if x=2 is a root of ax^2 - bx -x = 0, state the relationship connecting a,b, c and show that x=2 is also a root of
    bx^2 + cx - 8a = 0.

    the answer for the first part of the question is
    4a - 2b - c = 0.

    i need to know how to prove for the second part.
     
  2. jcsd
  3. Nov 26, 2003 #2
    bx2 + cx - 8a = 0 ???
    I can get bx2 + 2cx - 8a = 0 .....
     
  4. Nov 26, 2003 #3
    i do not type wrongly. however, can u tell me how you get that?
     
  5. Nov 26, 2003 #4
    am I mean or what

    anyway, I just multiplied your last result with -2. and yes, you were right, I was mistaken in the last post. It is
    bx2 + cx - 8a = 0

    I just get out of a meeting
     
    Last edited: Nov 26, 2003
  6. Nov 27, 2003 #5
    i still cant get what you mean.
     
  7. Nov 27, 2003 #6
    if you multiply by -2 you get
    -8a + 4b + 2c = 0

    now did you get it?
     
  8. Nov 27, 2003 #7
    tq. now i know what you mean.
     
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