- Home
- Standard 11
- Mathematics
10-2. Parabola, Ellipse, Hyperbola
medium
The equation of an ellipse whose focus $(-1, 1)$, whose directrix is $x - y + 3 = 0$ and whose eccentricity is $\frac{1}{2}$, is given by
A
$7{x^2} + 2xy + 7{y^2} + 10x - 10y + 7 = 0$
B
$7{x^2} - 2xy + 7{y^2} - 10x + 10y + 7 = 0$
C
$7{x^2} - 2xy + 7{y^2} - 10x - 10y - 7 = 0$
D
$7{x^2} - 2xy + 7{y^2} + 10x + 10y - 7 = 0$
Solution
(a) Let any point on it be $(x,y)$, then $\frac{{\sqrt {{{(x + 1)}^2}} + \sqrt {{{(y – 1)}^2}} }}{{\left| {\frac{{x – y + 3}}{{\sqrt 2 }}} \right|}} = \frac{1}{2}$
Squaring and simplifying, we get
$7{x^2} + 2xy + 7{y^2} + 10x – 10y + 7 = 0$.
Standard 11
Mathematics