Question
Question: The focus of parabola x<sup>2</sup> – 4x + 2y + 8 = 0 is...
The focus of parabola x2 – 4x + 2y + 8 = 0 is
A
(3/2, –2)
B
(5/2, –2)
C
(2, –3/2)
D
(2, –5/2)
Answer
(2, –5/2)
Explanation
Solution
x2 – 4x + 2y + 8 = 0
x2 – 4x + 4 = – 2y – 8 + 4
(x – 2)2 = – 2y – 4
̃ (x – 2)2 = – 2(y + 2) ̃ X2 = – 2Y
Focus
X = 0, Y = –1/2
x – 2 = 0, y + 2 = –1/2
x = 2, y = – 5/2
(2, –5/2)