Let E1 and E2 be two ellipses whose centers are at the origin. The major axes of E1 and E2 lie along the x-axis and the y-axis, respectively. Let S be the circle x2+y−12=2. The straight line x+y=3 touches the curves S, E1 and E2 at P, Q and R, respectively. Suppose that PQ=PR=223. If e1and e2are the eccentricities of E1 and E2 respectively, then the correct expression(s) is (are)
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a
e12+e22=4340
b
e1e2=7210
c
e12−e22=58
d
e1e2=34
answer is A.
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Detailed Solution
The line x+y=3 touches the circle x2+y−12=2 at PP is foot of perpendicular from 0,1 to x+y=3⇒ P1,2Since PQ=223=PR we have Q1+2232, 2−2232E1:x2a2+y2b2=1 with e12=a2−b2a2 ∴ a2+b2=9 x+y=3 touches E1⇒a2m2+b2=c2Since Q lies on E1, we have 259a2+169b2=1⇒ a2=5, b2=4∴e12=15 similarly R1−23, 2+23 lies on x2c2+y2d2=1 c
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Let E1 and E2 be two ellipses whose centers are at the origin. The major axes of E1 and E2 lie along the x-axis and the y-axis, respectively. Let S be the circle x2+y−12=2. The straight line x+y=3 touches the curves S, E1 and E2 at P, Q and R, respectively. Suppose that PQ=PR=223. If e1and e2are the eccentricities of E1 and E2 respectively, then the correct expression(s) is (are)