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Mathematics 13 Online
OpenStudy (anonymous):

how would i express the following quotient that is attached in a+bi form?

OpenStudy (anonymous):

\[\frac{ 5-2i }{ 3+2i }\]

OpenStudy (solomonzelman):

multiply top and bottom by conjugate. For a+bi the conjugate is a-bi So for 3+2i the conjugate is ?

OpenStudy (anonymous):

is a conjugate 2i ?

OpenStudy (solomonzelman):

in your case the conjugate is 3-2i. Multiply top and bottom times 3-2i and show me what you get.

OpenStudy (anonymous):

|dw:1401150105695:dw|

OpenStudy (anonymous):

\[\frac{ 5-2i }{ 3+2i }\times \frac{3-2i}{3-2i}=\frac{(5-2i)(3-2i)}{3^2+2^2}\] is a start

OpenStudy (anonymous):

this because \[(a+bi)(a-bi)=a^2+b^2\] now the denominator is a real number

OpenStudy (anonymous):

since \(3^2+2^2=9+4=13\) your only real job is to multiply \[(5-2i)(3-2i)\]for the top do you know how to do that?

OpenStudy (anonymous):

i only know how to do that as F.O.I.L

OpenStudy (anonymous):

ok that works

OpenStudy (anonymous):

\[(5-2i)(3-2i)=15-10i-6i+4i^2\] if you use that method then since \(i^2=-1\) you get \[15-4-16i=11-16i\]

OpenStudy (anonymous):

making your final answer \[\frac{11-16i}{13}=\frac{11}{13}-\frac{16}{13}i\]

OpenStudy (anonymous):

if you are going to do more than two or three of these, it might help to know what \[(a+bi)(c+di)=(ac-bd)+(ad+bc)i\]but "foil" works just as well, if you remember that \(i^2=-1\)

OpenStudy (anonymous):

ok, thank you so much for walking me through this problem, ill take this problem down into my notes for future reference :)

OpenStudy (anonymous):

yw

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