Question

What is the standard form of ( 5i ) (6-5i )
---------- ?
2i(-3+7i)
A) -111+126i
---------
40

B) -94+119i
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40

C)-94 +119i
------------
58

D) 94-119i
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58

Answer 1

start by multiplying out in your numerator and denominator to get:
\[\frac{ (5i)(6-5i) }{ (2i)(-3+7i) } = \frac{ 30i-25i^2 }{ -6i+17i^2 } = \frac{25+ 30i}{-17-6i}\]
then we need to simplify the bottom term. We can do this by multiplying by its complex conjugate
\[\frac{25+ 30i}{-17-6i}\ * \frac{ -17+6i }{ -17+6i }\]

try and finish from here!