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Questions  

 The equation of the ellipse having focus (1,1), directrix xy3=0 and eccentricity 1/2 is 

a
7x2+2xy+7y2−10x+10y+7=0
b
7x2+2xy+7y2+7=0
c
7x2+2xy+7y2+10x−10y−7=0
d
None of these

detailed solution

Correct option is A

Let P(x,y) be any point on the ellipse.  Then by definition, SP=ePM (where S is the focus and PM is  the distance of P from the directrix). So (x−1)2+(y+1)2=12x−y−32⇒ (x−1)2+(y+1)2=18(x−y−3)2⇒ 7x2+2xy+7y2−10x+10y+7=0

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