Turn on thread page Beta
    • Thread Starter
    Offline

    1
    ReputationRep:
    Question is:
    12 = [(47+j100) ((10-j25i2) / j100)] + j100i2

    Im stuck on the part:
    ((10-j25i2) / j100)

    Any help?

    Do I need to first look at it as:
    10/j100 - j25i2/j100
    • Thread Starter
    Offline

    1
    ReputationRep:
    I need to explain this better, basically i need to find out:

    (10 - j25) / j100
    Offline

    5
    ReputationRep:
    Not sure what you mean by the subscript i2?
    • Thread Starter
    Offline

    1
    ReputationRep:
    (Original post by doodlelizzie)
    Not sure what you mean by the subscript i2?
    I know by me putting in the subscript it confuses the situation without knowing the whole question, so thats why I replied again saying only:

    (10 - j25) / j100

    So I was asking do I approach it as:

    (10 / j100) - (j25 / j100)

    So then could I say:

    j0.1 - j0.25 ??????

    Im doing complex numbers but this is the 1st time I came across this setup
    Offline

    2
    ReputationRep:
    All you have to do is multiply the numerator and denominator by -j

    \frac{(10-25j)}{100j} \times\frac{-j}{-j}
    Offline

    16
    ReputationRep:
    (Original post by picklesmartyn)
    I know by me putting in the subscript it confuses the situation without knowing the whole question, so thats why I replied again saying only:

    (10 - j25) / j100

    So I was asking do I approach it as:

    (10 / j100) - (j25 / j100)

    So then could I say:

    j0.1 - j0.25 ??????

    Im doing complex numbers but this is the 1st time I came across this setup
    Can you remember in GCSE when to simplify expression such as \frac{2}{\sqrt{3}} you had to multiply top and bottom by \sqrt{3}? You just have to do the same thing here, but with j rather than \sqrt{3}.
    • Thread Starter
    Offline

    1
    ReputationRep:
    (Original post by jsMath)
    All you have to do is multiply the numerator and denominator by -j

    \frac{(10-25j)}{100j} \times\frac{-j}{-j}
    so that it then becomes:

    - j10 - 25 / 100

    which is then:

    0.25 - j0.1 ???????
    • Thread Starter
    Offline

    1
    ReputationRep:
    (Original post by brittanna)
    Can you remember in GCSE when to simplify expression such as \frac{2}{\sqrt{3}} you had to multiply top and bottom by \sqrt{3}? You just have to do the same thing here, but with j rather than \sqrt{3}.
    I do remember some simplifying fractions work, Ive just been out the subject for a while
    • Thread Starter
    Offline

    1
    ReputationRep:
    I know that when you get a scenario like:

    3+2i / 4-3i

    you multiply he numerator and denominator by the conjugate of the denominator:

    (3+2i / 4-3i) x (4+3i / 4+3i)

    But nowhere can I find an example like the one above where there is a single denominator that is a complex number aswell. Maybe im looking to hard into it!!
    Offline

    19
    ReputationRep:
    (Original post by picklesmartyn)
    I know that when you get a scenario like:

    3+2i / 4-3i

    you multiply he numerator and denominator by the conjugate of the denominator:

    (3+2i / 4-3i) x (4+3i / 4+3i)

    But nowhere can I find an example like the one above where there is a single denominator that is a complex number aswell. Maybe im looking to hard into it!!
    It's the same idea but the real part is zero - so you are multiplying by the complex conjugate.
    Offline

    2
    ReputationRep:
    (Original post by picklesmartyn)
    so that it then becomes:

    - j10 - 25 / 100

    which is then:

    0.25 - j0.1 ???????
    You were asking to simplify the above expression, then yes that would be the answer, if you were asked something else then kindly let us know

    You need to ask the right question in order to get the right answer,

    In general the idea is to get rid of the j in the den...
    • Thread Starter
    Offline

    1
    ReputationRep:
    (Original post by Muttley79)
    It's the same idea but the real part is zero - so you are multiplying by the complex conjugate.
    oh right so what your saying is:

    10 - j25 / j100

    is the same as:

    10 - j25 / 0 + j100

    so the conjugate is:

    0 - j100 ??????
    Offline

    2
    ReputationRep:
    (Original post by picklesmartyn)
    so that it then becomes:

    - j10 - 25 / 100

    which is then:

    0.25 - j0.1 ???????
    then you can multiply it by 100
    Offline

    19
    ReputationRep:
    (Original post by picklesmartyn)
    oh right so what your saying is:

    10 - j25 / j100

    is the same as:

    10 - j25 / 0 + j100

    so the conjugate is:

    0 - j100 ??????
    Yes
    • Thread Starter
    Offline

    1
    ReputationRep:
    (Original post by Muttley79)
    Yes
    Oh my god I knew it was something simple i forgot about the real part with respect to the imaginary part

    Thanks everyone
    Offline

    19
    ReputationRep:
    (Original post by picklesmartyn)
    Oh my god I knew it was something simple i forgot about the real part with respect to the imaginary part

    Thanks everyone
    Don't worry - it's easy to overlook
 
 
 

University open days

  1. University of Bradford
    University-wide Postgraduate
    Wed, 25 Jul '18
  2. University of Buckingham
    Psychology Taster Tutorial Undergraduate
    Wed, 25 Jul '18
  3. Bournemouth University
    Clearing Campus Visit Undergraduate
    Wed, 1 Aug '18
Poll
How are you feeling in the run-up to Results Day 2018?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.