MCQ
If the line $3x - 4y = \lambda $ touches the circle ${x^2} + {y^2} - 4x - 8y - 5 = 0$, then $\lambda $ is equal to
  • A
    $-35, -15$
  • $-35, 15$
  • C
    $35, 15$
  • D
    $35,-15$

Answer

Correct option: B.
$-35, 15$
b
(b) Accordingly, $\frac{{3(2) - 4(4) - \lambda }}{{\sqrt {{3^2} + {4^2}} }} $

$= \pm \sqrt {{2^2} + {4^2} + 5} $

$ \Rightarrow - 10 - \lambda = \pm 25$

$\Rightarrow \lambda = - 35,\;15$.

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