Question
If x + y + k = 0 is a tangent to the circle x2+y2 - 2x - 4y + 3 = 0 then k =
Answer: Option B
:
B
Radius = Distance from the centre C(1, 2) to x + y + k = 0
⇒ √1+4−3 = |1+2+k|√2 ⇒ |k+3| = 2 ⇒ k + 3 = ± 2 ⇒ k = -1, - 5
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B
Radius = Distance from the centre C(1, 2) to x + y + k = 0
⇒ √1+4−3 = |1+2+k|√2 ⇒ |k+3| = 2 ⇒ k + 3 = ± 2 ⇒ k = -1, - 5
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