Highly selective Backlog Qs for JEE MainMathematicsEllipse
Let S = x , y ∈ R 2 : y 2 1 + r - x 2 1 - r = 1 , where r ≠ ± 1 . Then S represents:
Options
- AAn ellipse whose eccentricity is 1 r + 1 , when r > 1 .
- BA hyperbola whose eccentricity is 2 r + 1 , when 0 < r < 1 .
- CAn ellipse whose eccentricity is 2 r + 1 , when r > 1
- DA hyperbola whose eccentricity is 2 1 - r , when 0 < r < 1
Correct answer
C. An ellipse whose eccentricity is 2 r + 1 , when r > 1
Step-by-step solution
Given y 2 1 + r - x 2 1 - r = 1 If r ∈ 0 , 1 then this curve is a hyperbola whose eccentricity is 1 + 1 - r 1 + r = 2 r + 1 . If r > 1 , then this curve is an ellipse whose eccentricity is 1 - r - 1 r + 1 = 2 r + 1 .