Question
Question: Locus of centre of variable circle tx<sup>2</sup> + ty<sup>2</sup> + 2(t<sup>2</sup> + 1)x – 2(t<sup...
Locus of centre of variable circle tx2 + ty2 + 2(t2 + 1)x – 2(t2 –1)y – 5t = 0 is a :
A
Straight line
B
Circle
C
Parabola
D
Hyperbola
Answer
Hyperbola
Explanation
Solution
Circle x2 + y2 +2t(t2+1)x – 2 t(t2–1)y – 5 = 0
centre (–t–t1,t–t1)
locus x2 – y2 = (t+t1)2 – (t–t1)2 = 4
Ž Hyperbola