RRB Group D Model Paper 10 with solutions

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Question : 47 of 100

Marks: +1, -0

If

x^2 + y^2 + 1/x^2+1/y^2

= 4 , then the value of

x^2 + y^2

is

2
4
8
16

Solution:

(1)

x^2 + y^2

+

1/x^2+1/y^2

= 4
=

x^2 + 1/x^2

- 2 +

y^2 +1/y^2

- 2 = 0

(x - 1/x)^2

+

(y -1/y)^2

= 0
⇒

(x - 1/x)

= 0 and

(y -1/y)

= 0
So, x = y = 1 and the Value of

x^2 + y^2

= 1 + 1 = 2.

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