Question

without actually calucating cube, evaluate 10³+11³-21³

Answer 1

10 ^3 +11^3 -21^3
= (10+11) ^3 - 21^3
=21^3 - 21^3
=0

Answer 2

a+b+c=0
so a^3+b^3+c^3=3abc
3×11×-21×10=-6930