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!

Complex number

  1. Apr 28, 2012 #1

    sharks

    User Avatar
    Gold Member

    The problem statement, all variables and given/known data
    Given that the real and imaginary parts of the complex number [itex]z=x+iy[/itex] satisfy the equation [itex](2-i)x-(1+3i)y=7[/itex]. Find x and y.

    The attempt at a solution
    I know it's quite simple. Just equate the real and imaginary parts, but i checked and redid it again, but the answer still evades me!
    [tex](2x-y-7) + i(-x-3y)=0
    \\2x-y-7=x
    \\x-y=7\, (1)
    \\-x-3y=y
    \\4y+x=0\, (2)
    \\x=28/5
    \\y=-7/5
    [/tex]
    I replaced in the original equation but i can't get 7 on the L.H.S.
    The correct answers: x=3 and y=-1.
     
  2. jcsd
  3. Apr 28, 2012 #2

    LCKurtz

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Why aren't those 0 on the right side?
     
  4. Apr 28, 2012 #3

    SammyS

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    When you write:
    [itex]2x-y-7=x[/itex]

    and

    [itex]-x-3y=y\ ,[/itex]​
    you are saying that
    [itex](2x-y-7) + i(-x-3y)=z\ .[/itex]​

    That's not what you're trying to solve !
     
  5. Apr 28, 2012 #4

    sharks

    User Avatar
    Gold Member

    I was confused about z=x+iy. I thought i had to compare the real and imaginary parts of z with those of the equation in order to solve it. I now realize that it has absolutely nothing to do with z. All i had to do was solve the equation independently and ignore whatever was given for z.

    Solving:[tex]2x-y=7
    \\-x-3y=0[/tex]I get the correct answers.

    Thank you, LCKurtz and SammyS. :smile:
     
    Last edited: Apr 28, 2012
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Complex number
  1. Complex numbers (Replies: 36)

Loading...