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MathsMediumMCQ2014 · 11 Apr Online

Q69.The set of all real values of λ for which exactly two common tangents can be drawn to the circles x2 + y2 −4x −4y + 6 = 0 and x2 + y2 −10x −10y + λ = 0 is the interval: (1) (12, 32) (2) (18, 42) (3) (12, 24) (4) (18, 48)

What This Question Tests

This question requires finding the centers and radii of two circles and then applying the conditions for exactly two common tangents based on the distance between their centers and their radii.

Concepts Tested

Equation of a circle (center and radius)Condition for number of common tangents

Formulas Used

(x-h)²+(y-k)²=r²

Distance between centers d = √((h₂-h₁)²+(k₂-k₁)²)

Conditions for common tangents (d=|r₁-r₂| for 3, d>r₁+r₂ for 4, d<|r₁-r₂| for 0, d=r₁+r₂ for 3, |r₁-r₂|<d<r₁+r₂ for 2)

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