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Mathematics 22 Online
OpenStudy (blondisaurus):

Multiplying complex numbers (HELP!!)

OpenStudy (blondisaurus):

\[\left( \sqrt{3 }i \right) \left( \sqrt{-3}i \right) - \sqrt{3}i (2-\sqrt{-3})\]

OpenStudy (blondisaurus):

Please show work :(

zepdrix (zepdrix):

\[\Large \left( \sqrt{3 }\;i \right) \color{royalblue}{\left( \sqrt{-3}\;i \right)} - \sqrt{3}\;i (2-\sqrt{-3})\] \[\Large \left( \sqrt{3 }\;i \right) \color{royalblue}{\left( \sqrt{3}\;i^2 \right)} - \sqrt{3}\;i (2-\sqrt{-3})\]

zepdrix (zepdrix):

Do you understand what I did in that step there?

OpenStudy (blondisaurus):

Oh because you took out the negative in the radical and added that i to the other one

zepdrix (zepdrix):

Multiplied the i's together :) Yes.

zepdrix (zepdrix):

If we multiply the first 2 brackets together we get, \[\Large 3\;i^3 - \sqrt{3}\;i (2-\sqrt{-3})\](multiply the 3's together and then the i's with one another)

OpenStudy (blondisaurus):

Ok, i follow. and the last term (before any multiplication) in the equation becomes minus radical 3i?

zepdrix (zepdrix):

ya that's a good idea probably.\[\Large 3\;i^3 - \sqrt{3}\;i (2-\sqrt{3}\;i)\]

zepdrix (zepdrix):

Distributing the sqrt3i to each term in the brackets is going to be a little messy. Do you think you can do it? :D

OpenStudy (blondisaurus):

Ill work it right now. Thanks so much btw!! @.@

OpenStudy (blondisaurus):

...and i already have a question... when distributing, does the two multiply the three (becoming radical 6i) or does it become 2 radical 3i

zepdrix (zepdrix):

\[\Large\bf\sf \sqrt2\cdot \sqrt3\quad=\quad \sqrt{2\cdot3}\quad=\quad \sqrt6\] \[\Large\bf\sf 2\cdot \sqrt3\quad\ne\quad \sqrt6\]\[\Large\bf\sf 2\cdot \sqrt3\quad=\quad 2\sqrt3\]

OpenStudy (blondisaurus):

Can more be done?

zepdrix (zepdrix):

Did you distribute the thing to the second term as well? Yes, lots more can be done ^^

OpenStudy (blondisaurus):

\[3i ^{3}-2\sqrt{3}i + \sqrt{6}i ^{2}\]

OpenStudy (blondisaurus):

9 my bad

zepdrix (zepdrix):

Ah good fix.

OpenStudy (blondisaurus):

then 3

OpenStudy (blondisaurus):

-3 times -2 so +6?

zepdrix (zepdrix):

\[\Large 3i ^{3}-2\sqrt{3}i + 3i ^{2}\]

OpenStudy (blondisaurus):

just -3....final answer

zepdrix (zepdrix):

whut? XD

OpenStudy (blondisaurus):

\[i ^{2}= -1 \]

zepdrix (zepdrix):

Oh for the last term? Ah good.

OpenStudy (blondisaurus):

so 3 times -1 equals -3?

zepdrix (zepdrix):

Ya we can simplify our last term using that, \[\Large 3i ^{3}-2\sqrt{3}i -3\]

zepdrix (zepdrix):

Do you know how to simplify i^3?

OpenStudy (blondisaurus):

sorta... i^2 times i equals -1 times i so it simplifies to negative i?

zepdrix (zepdrix):

yesss good.\[\Large -3i-2\sqrt{3}i -3\]

zepdrix (zepdrix):

And from here, I'm not really sure how we want to leave our answer. Does your teacher want it in the form `a+bi` ?

OpenStudy (blondisaurus):

I would assume so yes...is this the answer? No more could be done?

zepdrix (zepdrix):

Well that is a fine answer, yes. But if your teacher wants it in the form a+bi, then we should rewrite the real part first, and also factor an i out of each imaginary part.\[\Large -3+(-3-2\sqrt3)i\]See how it's in the form,\[\Large a+(b)i\]now?

OpenStudy (blondisaurus):

I do! Oh my god you dont know how much this helped. You are a god among men! A thousand thank yous! <3

zepdrix (zepdrix):

lol np \c:/

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