Question 59274
I haven't found an easy way of indicating cubed roots either.  I've used: \3/{{{sqrt(-54x^15*y^6)}}}
Find the perfect cubes within the radical sign.
\3/{{{sqrt(2*(-27)*(x^5)^3*(y^2)^3)}}}
\3/{{{sqrt(2*(-3)^3*(x^5)^3*(y^2)^3)}}}  Take the perfect cubes out and leave the rest inside the radical sign.
-3x^5*y^2\3/{{{sqrt(2)}}}
-3x^5y^2 the cubed root of 2.
Happy Calculating!!!