Find the equation of the ellipse with focus at `(-1,1)` and eccentricity 1/2 and directrix is x-y+3=0.

Explanation

We know that,

`SP=ePM`


`SP^2=e^2PM^2`

`i.e (SP)^2=1/4​(PM)^2`

`4(SP)^2=(PM)^2`

ie

`4[(x+1)^2+(y−1)^2]=((
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