1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Solving equation with two imaginary roots

  1. Dec 27, 2012 #1
    1. -xn2+2(k+2)x-9k=0
    Has two imaginary roots, what are the values of k?

    Attempted to break it down and use the quadratic formula but wasn't able to do it. Would like a pointer in the right direction of where to begin to solve it.

  2. jcsd
  3. Dec 27, 2012 #2


    Staff: Mentor

    look at the quadratic formula and ask yourself:

    What is the relationship between the polynomial coefficients to have imaginary roots?
  4. Dec 27, 2012 #3


    User Avatar
    Homework Helper
    Gold Member

    Yes, or I could say just look at that quadratic formula and ask yourself what terms must be real (take it that k is real) and what terms can be imaginary, it is a conceptual question not one of calculation.

    Have made one typo? - I suppose that should be maybe

    -x2 + 2(k+2)x -9k= 0

    Check you haven't made another. :wink:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook