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Question
Find centre and radius of the following circles
x2 + (y + 2)2 = 0
Solution
x2 + (y + 2)2 = 0
(i.e) x2 + y2 + 4y + 4 = 0
Comparing this equation with the general form x2 + y2 + 2gx + 2fy + c = 0
We get 2g = 0
⇒ g = 0
2f = 4
⇒ f = 2 and c = 4
Now centre = (– g, – f) = (0, – 2)
Radius = r
= `sqrt(g^2 + f^2 - "c")`
= `sqrt(0 + 4 - 4)`
∴ Centre = (0, – 2) and radius = 0
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