Question

(5-7b)^3+(9c-5a)^3+(7b-9c)^3

Answer 1

u have to use identity of a^3+b^3+c^3=3
abc
but before you have to prove that a + b + C is equal to zero

and by the terms
you can already see that all the terms of cancelling themselves so you will receive that a + b + C is equal to zero
then you can use identity of a cube plus b cube plus c cube is equal to 3 ABC..