The normal to the rectangular hyperbola xy=−c2 at the point ′t′1 meets the curve again at the point ′t′2. The value of t31⋅t2 is
A
1
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B
c
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C
−c
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D
−1
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Solution
The correct option is D−1 The equation of the normal t1is y−ct1=t21(x−ct1) If this passes through (ct2,ct2) ct2−ctt=t21(ct2−ct1) ⇒−1ttt2=t21⇒1+t3tt2=0 ⇒t31t2=−1 Hence, option 'D' is correct.