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: Simple complex number

  1. Jun 14, 2009 #1
    hey guys ive got a problem

    If z = 3− i and w = 1+3i, evaluate Im (z∗w)/(2z − 3w)

    my attempt... ill do top first (3+i)(1+3i)=3+9i+i+3i^2=10i???

    bottom=3-2i-3+9i=7i therefore answer equals 10/7 however answer is 3/13. could someone please help. thanks
  2. jcsd
  3. Jun 14, 2009 #2


    User Avatar
    Homework Helper

    (3-i)(1+3i) is the numerator, work that out again.

    Also for 2z, why did you have 3-2i instead of 2(3-i)=6-2i ?
  4. Jun 14, 2009 #3
    o soz that * is not a multiple sign its the conjurate sign i think. o yeh the bottom should be (6-2i)-(3+9i)=3+7i. is that right??
  5. Jun 14, 2009 #4


    User Avatar
    Homework Helper

    No [itex]-2i-9i \neq -7i[/itex]. The numerator has been calculated correctly.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook