Results 1 to 4 of 4

Math Help - Complex number

  1. #1
    Junior Member
    Joined
    Mar 2010
    From
    Malaysia
    Posts
    26

    Complex number

    Question is find all the roots :
    z^4 + 2z^3 + 5z^2 + 8z + 4 = 0

    I"m stuck at the beginning of this question. But i knew how to do this type of question and only does not know how to start.
    Thanks.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member
    earboth's Avatar
    Joined
    Jan 2006
    From
    Germany
    Posts
    5,829
    Thanks
    123
    Quote Originally Posted by wkn0524 View Post
    Question is find all the roots :
    z^4 + 2z^3 + 5z^2 + 8z + 4 = 0

    I"m stuck at the beginning of this question. But i knew how to do this type of question and only does not know how to start.
    Thanks.
    1. By trial and error you can see that z = -1 is a root of the equation. (Actually z = -1 is a double root of the equation) Use long division to get the remaining terms.

    z^4 + 2z^3 + 5z^2 + 8z + 4 = 0~\implies~(z+1)^2 \cdot (z^2+4)=0

    2. Go on!
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Mar 2010
    From
    Malaysia
    Posts
    26
    Sure, trying now
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Junior Member
    Joined
    Mar 2010
    From
    Malaysia
    Posts
    26
    I cant go on to next step...

    Before that i done this question
    z^4 + 2z^2 + 4 = 0

    Let x = z^2

    x^2 + 2x + 4 = 0

    a = 1 , b = 2, c = 4

    x = -b sqr b^2 -4ac / 2a

    then i can get the answers.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 1
    Last Post: October 2nd 2010, 01:54 PM
  2. Replies: 3
    Last Post: September 13th 2010, 11:13 AM
  3. Complex Number
    Posted in the Algebra Forum
    Replies: 2
    Last Post: June 18th 2009, 02:07 AM
  4. complex number
    Posted in the Algebra Forum
    Replies: 6
    Last Post: May 25th 2009, 11:13 AM
  5. Complex Number
    Posted in the Algebra Forum
    Replies: 3
    Last Post: September 16th 2006, 07:01 AM

Search Tags


/mathhelpforum @mathhelpforum