Explanation:

? (x³ + y³ + z³ – 3xyz)
= (x + y + z) (x² + y² + z² – xy – yz – zx)
=   (x + y + z) × 1/2 [(x – y)² + (y – z)² + (z – x)²]
On putting the values, we get
=  1000 × 1/2 [(332 – 333)² + (333 – 335)² + (335 – 332)²
=  1000 × 1/2  [1 + 4 + 9]
= 7000