Imaginary numbers help
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Imaginary numbers help

[From: ] [author: ] [Date: 12-01-09] [Hit: ]
and I dont know how to get from the problem to the answer. Help please?-Multiply both numerator and denominator by complex conjugate of denominator. Complex conjugate of (a + bi) is (a − bi),= 0.48 + 1.......
I got the problem
(8+3i)/(3-4i)
It says to write it in standard form. I don't know how to do this. I do know the answer is
12/25+41/25i=0.48+1.64i
I need to show work though, and I don't know how to get from the problem to the answer. Help please?

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Multiply both numerator and denominator by complex conjugate of denominator. Complex conjugate of (a + bi) is (a − bi), so complex conjugate of (3 − 4i) is (3 + 4i)

(8 + 3i) / (3 − 4i)

= (8 + 3i)(3 + 4i) / ((3 − 4i)(3 + 4i))

= (8 (3 + 4i) + 3i (3 + 4i)) / (3² − (4i)²)

= (24 + 32i + 9i + 12i²) / (9 − 16i²)

= (24 + 41i − 12) / (9 + 16)

= (12 + 41i) / 25

= 12/25 + 41/25 i

= 0.48 + 1.64 i

Mαthmφm

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The trick is to multiply by (3+4i)/(3+4i). Notice that this makes the denominator real. Once you've done that, everything else is straightforward.

Followup to the person who said to just use Wolfram Alpha:
Dude. It's a homework problem. The point is to learn how complex numbers work. Unless at least SOMEBODY in the next generation learns this stuff, then nobody will be around to program the next version of Wolfram Alpha. At least, nobody in this country . . .

-
(8 + 3i) (3 + 4i)
---------------------
(3 - 4i ) (3 + 4i)

24 + 41i - 12
--------------------
9 + 16

12 + 41i
--------------
25

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Use a website called wolframalpha.com
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