# Complex expressions

Hello I'm studying complex numbers for class and the question is stated as:
Let z=1+2i
Find:
a) 1/z^2
b) 1/z^3

I was thinking just to multiply by the conjugate (1-2i)^2 for (a) and similarly for (b).
Would that be correct in solving it?

## Answers and Replies

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mfb
Mentor
You can do that, right.
Alternatively, calculate 1/z first, and then calculate powers of that.

As this looks like homework, I moved your thread.

Oh thank you!
I apologize if I put it in the wrong thread!

Oh thank you!
I apologize if I put it in the wrong thread!
Firstly, let's establish what you are actually asking.

For example, the way you wrote it, 1/z^2 = $\frac{1}{z^2}$, NOT $(\frac{1}{z})^2$

EDIT: Please ignore. Complete brain-fart by me there!

Last edited:
mfb
Mentor
For example, the way you wrote it, 1/z^2 = $\frac{1}{z^2}$, NOT $(\frac{1}{z})^2$
Where is the difference?

Where is the difference?
Thanks. I simply cannot believe what I wrote in my previous post.

I blame lack of sleep...:zzz:

HallsofIvy