Question

Complex numbers,
https://www.dropbox.com/s/0tr5fu18nfua5n5/Screenshot%202013-11-23%2012.50.09.jpg

Answer 1

|x| is not differentiable at x=0

Answer 2

mode has a property
|a*b|=|a|*|b|

Answer 3

here y^2-x^2 is a polynomial so it is differentiable every where

Answer 4

but |xy|=|x|*|y| is not differentiable at x=y=0

Answer 5

except zero it is differentiable every where

Answer 6

@Christos