Question
Question: The foci of the ellipse, 25 (x + 1)<sup>2</sup> + 9 (y + 2)<sup>2</sup>= 225 are at –...
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) & (–2, 6)
C
(–1, –2) & (–2, –1)
D
(–1, –2) & (–1, – 6)
Answer
(–1, 2) and (–1, –6)
Explanation
Solution
(x + 1)2/9 + (y + 2)2/25 = 1, a = 3 X=x+1 \ b > a
b=5Y=y+2\foci=(0,±be),a2=b2 (1–e2)9
= 25 (1 – e2)
Že2=1–9/25Že=4/5\0,± be)
Ž(0±5(4/5)Ž(0,±4)
\X=0&Y = ± 4 x + 1 = 0 y + 2 = ± 4 (– 1, 2)
& (–1, –6)