# Complex Number in its simplest form

• Jul 21st 2010, 06:40 AM
Benji123
Complex Number in its simplest form
Hi all. Not sure whether this is correct or not and I would like some guidance! Thanks...

Given that z1 = 4-j5 and z2 = -3+j4, Find the compelx number z1/z1-z2 in its simplest form.

This is what I have...

z1 / (z1 -z2) = (4 - j5) / (4 - j5 +3 -j4) = (4-j5)/(7 - j9)

=[ (4-j5) x (7+j9) ] / [ (7-j9) x (7+j9) ]

=[ (4x7 - (-5) 9) + j(4x9+(-5)x7) ] / (49+81)

=(73+j)/130

=73/130+j/130
• Jul 21st 2010, 06:53 AM
eumyang
Looks right to me!
• Jul 21st 2010, 07:03 AM
Benji123
Thanks! I really had doubts about "z1 / (z1 -z2) = (4 - j5) / (4 - j5 +3 -j4) = (4-j5)/(7 - j9)"

I wasn't sure whether it was (4 - j5 + 3 - j4) or (4 - j5 + 3 +j4)
• Jul 21st 2010, 07:44 AM
pencil09
Quote:

Originally Posted by Benji123
Hi all. Not sure whether this is correct or not and I would like some guidance! Thanks...

Given that z1 = 4-j5 and z2 = -3+j4, Find the compelx number z1/z1-z2 in its simplest form.

$\frac{z1}{z1-z2}=\frac{4-5j}{4-5j-(-3+4j)}$
$\frac{z1}{z1-z2}=\frac{4-5j}{4-5j+(3-4j)}$
$\frac{z1}{z1-z2}=\frac{4-5j}{7-9j}$(Nerd)

-- hope it'll help --
• Jul 21st 2010, 10:08 AM
Benji123
So do I need to rationalize it or leave it as 4-5j/7-9j? Thanks.
• Jul 21st 2010, 10:21 AM
Unknown008
You rationalise it, yes. Your answer is good, do not worry (Happy)
• Jul 21st 2010, 10:28 AM
Benji123
Thanks people :D