Question

Without actually calculating the cubes, find the value of each of the following:

(28)3 + (-15)3 + (-13)3

Answer 1

(28)3 + (-15)3 + (-13)3

Let x = 28, y = −15, and z = −13

It can be observed that,

x + y + z = 28 + (−15) + (−13) = 28 − 28 = 0 It is known that if x + y + z = 0, then

X3 + Y3 +Z3

(28)3 + (-15)3 + (-13)3

= 3(28) + (-15) + (-13)

= 16380