1)
I type this in my calculator but I get domain error and I put in N, but it was wrong.
2)
I think it's |z| ? I'm not sure...
3)
Would this be $\displaystyle x^4$
-4 is a constant number and if it is raised to an even power, it will become positive.. hence, if you take an even root, it is always defined.. i think, check out how you typed it on you gadget.. Ü
for number three, by definition,
$\displaystyle \sqrt{x^8} = \sqrt{({x^4})^2} = |x^4|$
but x^4 is always positive, hence you can write it simply x^4