Question
Consider a family of circles which are passing through the point (–1, 1) and are tangent to x-axis. (h, k) are the co-ordinates of the centre of the circles, then the set of values of k is given by the interval
Answer: Option D
:
D
Since, circles are passing through the point (–1, 1) and touching X-axis, the equationof circles can be written as -
(h+1)2+(K–1)2=K2
h2+2h+2–2K=0
If h is real the Δ≥0
4- 4.1. (2 – 2K) ≥0
= 4 - 8 + 8k≥0
=8k≥4
=k≥12
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:
D
Since, circles are passing through the point (–1, 1) and touching X-axis, the equationof circles can be written as -
(h+1)2+(K–1)2=K2
h2+2h+2–2K=0
If h is real the Δ≥0
4- 4.1. (2 – 2K) ≥0
= 4 - 8 + 8k≥0
=8k≥4
=k≥12
Was this answer helpful ?
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