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

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

This is how I worked it out:

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

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

= $\displaystyle \sqrt{-9-16}$

= $\displaystyle \sqrt{-25}$

= $\displaystyle 5i$

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!!!