Thread: am I wrong here!?

1. am I wrong here!?

In the book I am working from I was asked to solve the following:

$\sqrt{(3+4i)(4i-3)}$

This is how I worked it out:

= $\sqrt{12i-9+16i^2-12i}$

= $\sqrt{-9+16i^2}$

= $\sqrt{-9-16}$

= $\sqrt{-25}$

= $5i$

Question, did I worked this problem wrong?! as I finished working it out I checked with the book's answer and I was given this as an answer {-1, 1}.

Could that book have a missprint or is it me?

Much thanks in advance!!!

2. How could $[-1,1]$ be an answer to this problem? We are looking for a number, not an interval. You may have looked at the wrong key. If not, the answer in the key is wrong.

3. Originally Posted by colby2152
How could $[-1,1]$ be an answer to this problem? We are looking for a number, not an interval. You may have looked at the wrong key. If not, the answer in the key is wrong.
..then it must have been a misprint on the part of the publishers!!

......OK, thank you very much, now I know this is going to be one hard semster