If the circles x^2+y^2+6x+8y+16=0 and x^2+y^2+2(3-√3)x+2(4-√6)y=k+6√3+8√6, k>0, touch internally at the point P(α ,β ), then (α +√3)^2+(β +√6)^2 is…
JEE Main 2022 — Mathematics Coordinate Geometry
2022integermedium
If the circles x2+y2+6x+8y+16=0 and x2+y2+2(3−3)x+2(4−6)y=k+63+86, k>0, touch internally at the point P(α,β), then (α+3)2+(β+6)2 is equal to _______.
Official previous-year question
Held on 25 Jul 2022 · Verified 6 Jul 2026.
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Solution
The circle x2+y2+6x+8y+16=0 has centre (−3,−4) and radius 9+16−16=3 units.
The circle x2+y2+2(3−3)x+2(4−6)y=k+63+86,k>0 has centre (3−3,6−4) and radius (3−3)2+(6−4)2+k+63+86=k+34
Given that these two circles touch internally, so
distance between their centres=∣difference of radii∣
3+6=∣k+34−3∣
⇒k+34−3=±3
Here, k=2 is only possible value (∵k>0)
Now the equation of common tangent to both the circles is given by 23x+26y+16+k+63+86=0
∵k=2 then equation becomes
x+2y+33+3+42=0⋯(i)
∵(α,β) are foot of perpendicular from (−3,−4) to this common tangent, then