Объяснение:
(c²+d²)³-3c²d²(c²+d²)=
=(c²)³+3(c²)²d²+3c²(d²)²+(d²)³ -3c^4d²-3c²d^4=
=c^6+3c^4d²+3c²d^4+d^6-3c^4d²-3c²d^4= c^6+d^6
