COMEDK · Maths · 12. Circle
The number of common tangent to the circle \(x^2+y^2=9\) and \(x^2+y^2-6 x-8 y+21=0\)
- A 0
- B 1
- C 3
- D 4
Answer & Solution
Correct Answer
(C) 3
Step-by-step Solution
Detailed explanation
If equation of circle is \(x^2+y^2+2 g x+2 f y+c=0\) Then, centre \(\equiv(-g,-f)\) \(\text { radius }=\sqrt{g^2+f^2-c}\) \(\Rightarrow\) Centre of first circle \(\equiv(0,0)\) radius of first circle \(\equiv 3\) \(\Rightarrow\) Centre of second circle \(\equiv(3,4)\) radius of…
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