SSC CGL 31 Aug 2016 Paper

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Question : 66 of 100

Marks: +1, -0

If

(x+1/x)^2

= 3 , then the value of

(x^3+1/x^3)

is

0
1
2
- 1

Solution:

(x+1/x)^2

= 3
∴ x +

1/x

=

√3

On cubing both sides,

(x+1/x)^3

=

(√3)^2

⇒

x^3+1/x^3

+ 3

(x+1/x)

=

3√3

⇒

x^3+1/x^3

+

3√3

=

3√3

⇒

x^3+1/x^3

=

3√3 - 3√3

= 0

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