SSC CGL 16 Aug 2015 Shift 2 Paper

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Question : 130 of 200

Marks: +1, -0

If x = z = 225 and y = 226 then the value of :

x^3 + y^3 + z^3

– 3xyz is

765
676
576
674

Solution:

x = z = 225, y = 226
∴ x + y + z = 225 + 226 + 225 = 676
∴

x^3 + y^3 + z^3

– 3 xyz =

1/2

(x + y + z) [

(x-y)^2 + (y-z)^2 + (z-x)^2

]
=

1/2

× 676 [

(225-226)^2

+

(226-225)^2

+

(225-225)^2

]
=

1/2

× 676 × (1 + 1) = 676

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