. The foci of the ellipse


25 (x + 1)2 + 9 (y + 2)2 = 225 are at

A. (-1, 2) and (-1, -6)

B. (-2, 1) and (-2, 6)

C. (-1, -2) and (-2, -1)

D. (-1, -2) and (-1, -6).

 

Best Answer

Ans: A

Sol: The  given equation is  25 ( x+ 1)2 + 9 ( y + 2) 2 = 225

were

Centre  of the ellipse º ( -1, -2 )

and a = 3 ,   b =  5, so  that a< b Þ  3 = was

or e2   =  1-  9/ 25 =  16/25 Þ  e =  4/ 5

Hence  foci  are ( -1,  -2 - 5´ 4/5)  and  ( -1 ,  -2 + 5 ´ 4/5)

i.e.  foci   are  (-1 ,  -6 )  and  (-1, 2) .

Hence (A) is the correct answer. 

 

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