Rewrite with positive exponents.Assume that even roots are nonnegative quanities and all denominators are nonzero...(4xy^-2)^-2
4^-2 = 1/4^2 = 1/16
x^-2 = 1/x^2
(y^-2)^-2 = (1/y^2)^-2= = y^4
so
y^4/(16 x^2)
x^-2 = 1/x^2
(y^-2)^-2 = (1/y^2)^-2= = y^4
so
y^4/(16 x^2)