Question 1089285
square root of 512m4n3; it is not quite clear what do you have

I guess you have {{{sqrt(512m^4n^3)}}}

if so, than

{{{sqrt(512m^4n^3)}}}

{{{sqrt(16^2*2(m^2)^2n^2*n)}}}

{{{16m^2n*sqrt(2n)}}}