Find 'i'

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February 7th 2009, 10:01 PM
delicate_tears

Find 'i'- where i^2 = -1

http://i77.photobucket.com/albums/j5...maths_snap.png
The answer should be -7/5 - 17i/10 but somehow I couldn't figure it out.

http://i77.photobucket.com/albums/j5...ars/Noname.png

The answer should be -2 -3i/2 but I always get -2 +3i/2 for my answer. Help please?

i is an imaginary number. That is i^2 = -1
February 7th 2009, 10:17 PM
smmmc

when you say find 'i' do you mean make i the subject? because the answer is -7/5 - 17i/10, which has 'i' in it .
February 7th 2009, 10:43 PM
james_bond

$\frac {8-3i-4-6i}{2+4i}=\frac {4-9i}{2+4i}=a+bi\rightarrow 4-9i=(2+4i)(a+bi)=2a+4ai+2bi-4b=$ $2a-4b+(4a+2b)i$ So $4=2a-4b$ and $-9=4a+2b$ . Can you continue from here?

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