SSC CGL Model Paper 16

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Question : 64 of 100

Marks: +1, -0

If

2x +1/{2x} = 2

, then what is the value of

√{2(1/x)^4+(1/x)^5 }

?

1
2
4
8

Solution:

2x +1/{2x} = 2

⇒

4 x^ 2 + 1 = 4 x

⇒

4 x ^2- 4 x + 1 = 0

⇒

4 x^ 2 - 2 x - 2 x + 1 = 0

⇒

2 x (2 x -1 ) -1 (2 x -1 ) = 0

⇒

(2 x -1 ) (2 x - 1 ) = 0

∴

x=1/2⇒1/x=2

√{2(1/x)^4+(1/x)^5 }

=√{2(2)^4+(2)^5

=√{32+32}

=√64=8

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