SSC CGL 9 Aug 2015 Shift 2 Paper

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Question : 139 of 200

Marks: +1, -0

If x +

1/x

= 2 then the value of

x^{12}-1/x^{12}

is

2
– 4
0
4

Solution:

x +

1/x

= 2
⇒

{x^+1}/x

= 2 ⇒

x^2

+ 1 = 2x
⇒

x^2

– 2x + 1 = 0
⇒

(x – 1)^2

= 0
⇒ x – 1 = 0
⇒ x = 1
∴

x^{12}-1/x^{12}

= 1 + 1 = 2

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