If x + y = 15, then (x – 10)3 + (y

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If x + y = 15, then (x – 10)³ + (y – 5)³ is

1. 25
2. 125
3. 625
4. 0

Correct Option: D

x + y = 15
⇒ (x – 10) + (y – 5) = 0
∴ (x – 10)³ + (y – 5)³ = (x – 10 + y – 5)³ – 3(x – 10)(y – 5)(x – 10 + y – 5) = 0
[∴ a³ + b³ = (a + b)³ – 3ab (a + b)]