The circle $x^{2} + y^{2} = 9$ and $x^{2} + y^{2} - 12 y + 27 = 0$ touch each other. The equation of their common tangent is

4 y = 9

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y = 3

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y = - 3

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x = 3

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Solution

The correct option is C $y = 3$
Equation of common tangent :
$s_{1} - s_{2} = 0$

$(x^{2} + y^{2} - 9) - (x^{2} + y^{2} - 12 y + 27) = 0$

$- 9 + 12 y - 27 = 0$

$12 y = 36 \Rightarrow y = 3$

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The circle x2+y2=9 and x2+y2−12y+27=0 touch each other. The equation of their common tangent is

The correct option is C y=3Equation of common tangent :s1−s2=0(x2+y2−9)−(x2+y2−12y+27)=0−9+12y−27=012y=36⇒y=3

The circle $x^{2} + y^{2} = 9$ and $x^{2} + y^{2} - 12 y + 27 = 0$ touch each other. The equation of their common tangent is

The correct option is C $y = 3$
Equation of common tangent :
$s_{1} - s_{2} = 0$

$(x^{2} + y^{2} - 9) - (x^{2} + y^{2} - 12 y + 27) = 0$

$- 9 + 12 y - 27 = 0$

$12 y = 36 \Rightarrow y = 3$