Q: If e and e_{1} are the eccentricities of the hyperbola xy = c^{2} and x^{2} – y^{2} = c^{2}, then e^{2} + e_{1}^{2} is equal to

(A) 1

(B) 4

(C) 6

(D) 8

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Ans: (B)

Sol: e = √2 , e

_{1}= √2⇒ e^{2} + e_{1}^{2} = 4.

Hence (B) is the correct answer.