Equation of hyperbola is a2x2− b2y2=1 Directrix: x=5−9 and corresponding foci (−5,0) ⇒−ea=−59 and −ae=−5 ⇒59e2=5⇒e=925=35⇒a=3 ∴b2=a2(e2−1)=9(925−1)=16 Hyperbola 9x2−16y2=1 (α,25) lie on it ⇒9α2−1620=1⇒α2=1636×9=481 Product for distance of (x1y1) from the two foci =(ex1+a)∣ex1−a∣=e2x12−a2 For (α,25)⇒P=925⋅481−9=4189 4P=189