SSC CGL 6 Sep 2016 Paper

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Question : 58 of 100

Marks: +1, -0

If 5x +

1/x

= 10, then

x^2 + 1/{25x^2}

is equal to

2 $1/5$
3 $1/5$
3 $3/5$
2 $3/5$

Solution:

5x

+ 1/x

= 10
On dividing by 5,
x +

1/{5x}

= 2
On squaring both sides,

(x+1/{5x})^2

= 4
⇒

x^2+1/{25x^2}

+ 2x ×

1/{5x}

= 4
⇒

x^2 + 1/{25x^2}

= 4 -

2/5

=

{20-2}/5

=

{18}/5

= 3

3/5

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