SOLUTION: I don't understand how to preform the operations with complex numbers like with; (6-5i)(4-9i) and also like; please help, I need to get my grade back to a B by tmoorrow... 2+3i/

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Question 694095: I don't understand how to preform the operations with complex numbers like with;
(6-5i)(4-9i) and also like; please help, I need to get my grade back to a B by tmoorrow...
2+3i/
4-5i

Found 2 solutions by stanbon, josmiceli:
Answer by stanbon(75887)   (Show Source): You can put this solution on YOUR website!
(6-5i)(4-9i)
Use FOIL:
F: 6*4 = 24
O:6*-91 = -54i
I:-5i*4 = -20i
L:-5i*-9i = -45
------
Combine to get:
-21 -74i
====================
(2+3i)/(4-5i)
----
Multiply numerator and denominator by (4+5i) to get:
-----
= [(2+3i)(4+5i)]/[(4-5i)(4+5i)]
-------
= [8-15 + 21i+10i] / [16+25]
------
= [-7+31i]/41
=====================
Cheers,
Stan H.

Answer by josmiceli(19441)   (Show Source): You can put this solution on YOUR website!
you have to know that


------------


------------


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To multiply , you need
to know the more basic operation

You're doing the same thing with operations on



---------------

Multiply top and bottom by






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It's easy to make a mistake on these, but
I hope you get the idea

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