1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Quadratic Equation

  1. Apr 10, 2008 #1
    1. The problem statement, all variables and given/known data

    If one root of a quadratic equation with rational co-efficient is (2^(1/2)+1) , then find the quadratic equation.

    2. Relevant equations


    3. The attempt at a solution

    Well, I cant quite understand this question. Please help me to understand what is given in the following statemnt.
  2. jcsd
  3. Apr 10, 2008 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    If the only square root in the solution is [itex]\sqrt{2}[/itex], what must d be? Since the only difference between roots of a quadratic equation is that [itex]\pm[/itex] before the square root, what must the other root be?

    Another, more "sophisticated" method:
    Any quadratic, [itex]ax^2+ bx+ c[/itex] can be written [itex]a(x- x_0)(x- x_1)= ax^2- a(x_0+x_1)+ ax_0x_1[/itex] where [itex]x_0[/itex] and [itex]x_1[/itex] are roots of the equation. If one root is [itex]1+ \sqrt{2}[/itex] what must the other be so that both [itex]x_0+ x_1[/itex] and [itex]x_0x_1[/itex] are rational?
    Last edited: Apr 10, 2008
  4. Apr 10, 2008 #3
    Well, Please check this. I think the othr root is 1-(2^1/2). thre fore the quadratic equation is x^2-2x-1=0
    Am I right?
  5. Apr 10, 2008 #4


    User Avatar
    Staff Emeritus
    Science Advisor

    Yes, that is correct.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Quadratic Equation
  1. Quadratic equation (Replies: 6)

  2. Quadratic equation (Replies: 11)

  3. Quadratic equations (Replies: 11)

  4. Quadratic equations (Replies: 1)

  5. Quadratic Equation (Replies: 6)