pre cal... complex numbers

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candy101

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it says find i... am i suppose to Multiply by the Conjugate of the denominator?

4+5i/ 2-3i


this is how i think it should be done
4+5i/ 2-3i and then i multiply 2+3i on both the top and bottom

4+5i/ 2-3i * 2+3i/2+3i is this correct? if so im i dont know what else to do
 
candy101 said:
it says find i... am i suppose to Multiply by the Conjugate of the denominator?

4+5i/ 2-3i


this is how i think it should be done
4+5i/ 2-3i and then i multiply 2+3i on both the top and bottom

(4+5i)/ (2-3i) * (2+3i)/(2+3i) is this correct? if so im i dont know what else to do
Click to expand...

First - you need to use parentheses as shown to be correct.

Now multiply numarator with numarator and denominator with denominator.

And simplify ....
 
To learn how to rationalize a complex denominator, try here. If you need first to learn how to multiply complex numbers, try here. :wink:
 
candy101 said:
it says find i... am i suppose to Multiply by the Conjugate of the denominator? 4+5i/ 2-3i
Click to expand...
Here is one of the most important ideas in complex numbers.
\(\displaystyle \frac{1}{z} = \frac{{\overline z }}{{\left| z \right|^2 }}~~~\). Thus \(\displaystyle \frac{1}{{2 - 3i}} = \frac{{2 + 3i}}{{13}}\)

So multiply that by \(\displaystyle 4+5i\).
 
pka said:
candy101 said:
it says find i... am i suppose to Multiply by the Conjugate of the denominator? 4+5i/ 2-3i
Click to expand...
Here is one of the most important ideas in complex numbers.
\(\displaystyle \frac{1}{z} = \frac{{\overline z }}{{\left| z \right|^2 }}~~~.\) Thus \(\displaystyle \frac{1}{{2 - 3i}} = \frac{{2 + 3i}}{{13}}\)

So multiply that by \(\displaystyle 4+5i\).
Click to expand...
 
so i think i got the answer..just wanna make sure its right



my ans. is -11+16i/13

( :| hope its right)
 
candy101 said:
so i think i got the answer..just wanna make sure its right



my ans. is -11+16i/13

( :| hope its right)
Click to expand...

My answer is : ( -7 + 22i )/13
 
o gosh i redid and i got the same ans. as u...i made a mistake with the calculation :oops:


thanks...
 
candy101 said:
it says find i... am i suppose to Multiply by the Conjugate of the denominator?

4+5i/ 2-3i


this is how i think it should be done
4+5i/ 2-3i and then i multiply 2+3i on both the top and bottom

4+5i/ 2-3i * 2+3i/2+3i is this correct? if so im i dont know what else to do
Click to expand...

Did anybody figure out exactly what did the question ask?

If I had to take a wild-guess - that would be - Find the coefficient of i....
 
candy101 said:
its about Multiplying complex number..
Click to expand...

But what was the exact question? The answer will be different with different question.
 
idk we might go over it in class and if the answer is the same then i guess thats what it is...i will let you know..(if we go over it in class)
 
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