what is the following sum? assume x greater-than-or-equal-to 0 and y greater-than-or-equal-to 0startroot x squared y cubed endroot 2 startroot x cubed y superscript 4 baseline endroot x y startroot y endrootx squared y squared startroot y endroot minus 2 x y squared startroot x endroot2 x y startroot y endroot 2 x y squared startroot x endroot4 x y startroot x superscript 5 baseline y superscript 8 baseline endroot2 x y startroot x y endroot