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Math Help - hi just need a quick hand not the answer please

  1. #1
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    hi just need a quick hand not the answer please

    the question is
    z = (2-i)
    w=(5+3i)
    so work out
    a)zw
    b)z/w
    both of which i can do with no problem but the last bit is
    c) |w|
    can some one please tell me what the 2 straight lines mean on each side of the w thank you 4 ur time and any help

    also im a bit stuck with this simultaneous equation i have never done them with fractions in i think it is easy but i might just be looking at it in the wrong way
    4/x+1/y=5/3
    1/x-3/y=3/2
    should i be trying to get it on 1 line so times it by xy any help would be very greatfull thank you
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  2. #2
    Super Member
    earboth's Avatar
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    Quote Originally Posted by alpharebel10 View Post
    the question is
    z = (2-i)
    w=(5+3i)
    so work out
    a)zw
    b)z/w
    both of which i can do with no problem but the last bit is
    c) |w|
    can some one please tell me what the 2 straight lines mean on each side of the w thank you 4 ur time and any help
    |w| is the absolute value of w

    also im a bit stuck with this simultaneous equation i have never done them with fractions in i think it is easy but i might just be looking at it in the wrong way
    4/x+1/y=5/3
    1/x-3/y=3/2
    ...
    Set r = \frac1x and s = \frac1y then your system of equations becomes:

    \left|\begin{array}{l}4r+s=\frac53 \\r-3s=\frac32\end{array}\right.

    Solve for r and s and re-substitute to calculate x and y.
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  3. #3
    Senior Member
    Joined
    Nov 2007
    Posts
    329
    Quote Originally Posted by alpharebel10 View Post
    c) |w|
    can some one please tell me what the 2 straight lines mean on each side of the w thank you 4 ur time and any help
    See here.
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