InterviewSolution
Saved Bookmarks
| 1. |
Show that line x – 3y – 4 = 0 touches ellipse 3x2 + 4y2 = 20. |
|
Answer» Equation of line, x – 3y – 4 =0 ⇒ x = 3y + 4 Equation of ellipse, 3x2 + 4y2 = 20 Putting value of x from (i) in eqn. (ii), 3(3y + 4)2 + 4y2 = 20 ⇒ 3(9y2 + 24y + 16) + 4y2 – 20 = 0 ⇒ 27y2 + 72y + 48 + 4y2 – 20 = 0 ⇒ 31y2 + 72y + 28 = 0 Line will touch eqn. (ii) if (72)2 – 4(31 )(28) = 0 ∴ (72)2 – 4 × 31 × 28 = 5184 – 3472 = 1712 ≠ 0 Thus, given line will not be touch given ellipse. ∴ Given equation is wrong. |
|