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  1. If x = z = 225 and y = 226 then the value of x3 + y3 + z3 - 3xyz is :
    1. 765
    2. 676
    3. 576
    4. 674
Correct Option: B

Using Rule 22,
x = z = 225, y = 226
∴ x + y + z = 225 + 226 + 225 = 676

∴ x3 + y3 + z3 – 3 xyz =
1
(x + y + z) [ (x - y)2 + (y - z)2 + (z - x)2 ]
2

⇒ x3 + y3 + z3 – 3 xyz =
1
× 676 × [ (225 – 226)2 + (226 – 225)2 + (225 – 225)2 ]
2

⇒ x3 + y3 + z3 – 3 xyz =
1
× 676 × (1 + 1) = 676
2



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