- #1

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Z2=7+2i express (1/Z1)-(1/Z2) in form a+bi

SOMEONE plzzzzzzz HELP ME!!! I dont have a clue as to how to do this

What do I do?

Where do I start?

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- Thread starter aisha
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- #1

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Z2=7+2i express (1/Z1)-(1/Z2) in form a+bi

SOMEONE plzzzzzzz HELP ME!!! I dont have a clue as to how to do this

What do I do?

Where do I start?

- #2

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Hope that helps! :)

- #3

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Do you know what a "complex conjugate" is?

- #4

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Parth Dave said:Do you know what a "complex conjugate" is?

Yes I do it is the opposite sign well when dividing you take the denominator and divide by the conjugate I know that but in this question I dont know what to do or what order to do it in plz help me plzzz

- #5

BobG

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nolachrymose described it pretty well.nolachrymose said:

Hope that helps! :)

If you substituted

[tex]\frac{5}{\sqrt{-1}+2}[/tex],

and multiplied by the conjugate, you'd get:

[tex]\frac{5(\sqrt{-1}-2)}{-1 - 4} = 2 - \sqrt{-1}[/tex]

The

- #6

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- #7

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- #8

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a)89/24-73/24i

b)89/24+73/24i

c)-89/24+73/24i

d)89/24i-73/24

I dont get anything close to these when i take those two answers and subtract them. Please help me Ive been doing this one forever

- #9

BobG

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So what did you get? Something close to

[tex]\frac{89+73i}{530}[/tex]

- #10

BobG

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[tex]\frac{1}{3-i}-\frac{1}{7+2i}[/tex]

[tex]\frac{3+i}{9-(-1)}-\frac{7-2i}{49-(-4)}[/tex]

[tex]\frac{3+i}{10}-\frac{7-2i}{53}[/tex]

[tex]\frac{(159+53i)-(70-20i)}{530}[/tex]

[tex]\frac{89+73i}{530}[/tex]

Or:

[tex]\frac{1}{3-i}-\frac{1}{7+2i}[/tex]

[tex]\frac{7+2i}{(3-i)(7+2i)}-\frac{3-i}{(3-i)(7+2i)}[/tex]

[tex]\frac{7+2i-3+i}{(21-(-2))+(6i-7i)}[/tex]

[tex]\frac{4+3i}{23-i}[/tex]

[tex]\frac{(4+3i)(23+i)}{(23-i)(23+i)}[/tex]

[tex]\frac{(92+(-3))+(69i+4i)}{529-(-1)}[/tex] Here's where they made their mistake

[tex]\frac{89+73i}{530}[/tex]

You can break this up into two separate fractions, if you want:

[tex]\frac{89}{530}+\frac{73}{530}i[/tex]

Instead of multiplying (23-i)(23+i) and getting 529+1, they got 23+1. So, the answer they most likely picked is (b)

- #11

arildno

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- #12

BobG

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A flaw?! Or is it really a hidden 'feature'? (how come we don't have a 'shifty eyed' smilie?)arildno said:

"B's for everyone who answers all the questions right. A's for everyone who catches my error and figures out exactly where I made my mistake!"

- #13

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BobG said:

So what did you get? Something close to

[tex]\frac{89+73i}{530}[/tex]

Well my answer was (89-33i)/530

u are right that the question that was correct was b with the error in it. I think our answers are different because when u expanded -10(7-2i)/530 u wrote -70-20i shouldnt this be -70+2i because of the two negative signs? I will for sure point this question out to my teacher maybe she will give me an "A" lol for cathching the errors. Thanks so much I thought I was doing this totally wrong, but I guess not thanks again ur my HERO

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