RRB Group-D Model Paper 15 with answers for online practice

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Question : 78 of 100

Marks: +1, -0

If

x−1/x=10

, then

(x+1/x)

is equal to

$5√26$
$2√26$
$3√26$
$4√26$

Solution:

x−1/x=10

⇒

x^2−2+1/x^2=100

⇒

x^2+1/x^2=102

(x+1/x)^2=x^2+2+1/x^2=102+2=104

⇒

x+1/x=√104=2√26

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