$(9$ pts$.)$

$2.$ In each part below determine the value of the given limit or show that the limit does not exist.

$($i$)\underset{(x,y)(0,0)}{lim}\frac{x^2-4xy2y^2}{x^2{y}^2}$

$($ii$)\underset{(x,y)(0,0)}{lim}\frac{x^3{y}^2}{(x^2{y}^2{)}^2}$

$($iii$)\underset{(x,y)(0,0)}{lim}\frac{x{y}^3}{x^2{y}^6}$