Circles x^2 + y^2 + 4x + d = 0, x^2 + y^2 + 4fy + d = 0 touch eac… - Vidyadip

MCQ

Circles $x^2 + y^2 + 4x + d = 0, x^2 + y^2 + 4fy + d = 0$ touch each other, if

A
$f\,\, = \,\, \pm \,\,2\,\sqrt {4\,\, + \;\,d} $
B
$f\,\, = \,\, \pm \,\,\frac{2}{{\sqrt {4\,\, - \,\,d} }}$
C
$f\,\, = \,\, \pm \,\,\sqrt {\frac{d}{{\left( {4\,\, + \;\,d} \right)}}} $
✓
$f\,\, = \,\, \pm \,\,\sqrt {\frac{d}{{\left( {4\,\, - \,\,d} \right)}}} $

✓

Answer

Correct option: D.

$f\,\, = \,\, \pm \,\,\sqrt {\frac{d}{{\left( {4\,\, - \,\,d} \right)}}} $

d

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