SSC CGL 26 Oct 2014 Shift 2 Paper

© examsiri.com

Question : 114 of 200

Marks: +1, -0

If x +

1/x

= 5 , then

x^6+1/x^6

is

12098
12048
14062
12092

Solution:

x +

1/x

= 5
On cubing both sides,

(x+1/x)^3

=

5^3

⇒

x^3+1/x^3

+ 3x .

1/x(x+1/x)

= 125
⇒

x^3+1/x^3

+ 3 × 5 = 125
⇒

x^3+1/x^3

= 125 - 15 = 110
On squaring both sides,

x^6+1/x^6

+ 2 .

x^3 . 1/x^3

= 12100
⇒

x^6+1/x^6

= 12100 - 2
= 12098

© examsiri.com

Go to Question:

Prev Question

Next Question