SSC CGL 5 Aug 2017 Shift 1 Paper

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Question : 63 of 100

Marks: +1, -0

If

x +1/x= 4

, then what is the value

x ^6+1/x^6

?

52
256
1026
2702

Solution:

x +1/x= 4

On squaring both sides,

x^2 +1/x^2+2=16

x^2 +1/x^2 =14

On cubing both sides,

x ^6+1/x^6+3x^2 ×1/x^2(x^2+1/x^2)=(14)^3

⇒

x^6+1/x^6+3 ×(14)=2744

∴

x ^6+1/x^6=2744-42=2702

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