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JEE Main 202225 JulyEvening Shift
Exam
JEE Main
Year
2022
Date
25 July
Shift
Evening Shift
Subject
Mathematics
Chapter
Circle

JEE Main 2022 · 25 July · Evening Shift · Mathematics · Circle

If the circles x ^ 2 + y ^ 2 + 6x + 8y + 16 = 0 and x ^ 2 + y ^ 2 +...

If the circles x2+y2+6x+8y+16=0{x}^{2} + {y}^{2} + 6x + 8y + 16 = 0 and x2+y2+2(3−3)x+2(4−6)y=k+63+86{x}^{2} + {y}^{2} + 2\left(3 - \sqrt{3}\right)x + 2\left(4 - \sqrt{6}\right)y = k + 6\sqrt{3} + 8\sqrt{6}, k>0k > 0, touch internally at the point P(α,β)P\left(\alpha, \beta\right), then (α+3)2+(β+6)2{\left(\alpha + \sqrt{3}\right)}^{2} + {\left(\beta + \sqrt{6}\right)}^{2} is equal to _______.

Correct answer

0

Step-by-step solution

The circle x2+y2+6x+8y+16=0{x}^{2} + {y}^{2} + 6x + 8y + 16 = 0 has centre \left(- 3, - 4\right)andradiusand radius\sqrt{9 + 16 - 16} = 3units.</p><p>Thecircleunits.</p><p>The circle{x}^{2} + {y}^{2} + 2\left(3 - \sqrt{3}\right)x + 2(4−6)y=k+63+86,k>0\left(4 - \sqrt{6}\right)y = k + 6\sqrt{3} + 8\sqrt{6}, k > 0 has centre \left(\sqrt{3} - 3, \sqrt{6} - 4\right)andradiusand radius\sqrt{{\left(\sqrt{3} - 3\right)}^{2} + {\left(\sqrt{6} - 4\right)}^{2} + k + 6\sqrt{3} + 8\sqrt{6}} = \sqrt{k + 34}</p><p>Giventhatthesetwocirclestouchinternally,so</p><p>distancebetweentheircentres</p><p>Given that these two circles touch internally, so</p><p>distance between their centres= \left|\text{differenceofofradii}\right|</p><p></p><p>\sqrt{3 + 6} = \left|\sqrt{k + 34} - 3\right|

⇒k+34−3=±3⇒ \sqrt{k + 34} - 3 = \pm 3

Here, k=2k = 2is only possible value \left(∵ k > 0\right)

Nowtheequationofcommontangenttoboththecirclesisgivenby23x+26y+16+k+63+86=0the equation of common tangent to both the circles is given by2\sqrt{3}x + 2\sqrt{6}y + 16 + k + 6\sqrt{3} + 8\sqrt{6} = 0

∵k=2∵ k = 2 then equation becomes

x+2y+33+3+42=0⋯(i)x + \sqrt{2}y + 3\sqrt{3} + 3 + 4\sqrt{2} = 0 ⋯ \left(i\right)

∵(α,β)arefoot∵ \left(\alpha, \beta\right) are foot of perpendicularfrom(−3,−4)tothiscommontangent,then</p><p>α+31=β+42=−(−3−42+3+42+33)1+2perpendicular from \left(- 3, - 4\right) to this common tangent, then</p><p>\dfrac{\alpha + 3}{1} =\dfrac{\beta + 4}{\sqrt{2}} = \dfrac{- \left(- 3 - 4\sqrt{2} + 3 + 4\sqrt{2} + 3\sqrt{3}\right)}{1 + 2}

∴α+3=−3 and  β+42=−3∴ \alpha + 3 = - \sqrt{3} \text{\text{ and } } \dfrac{\beta + 4}{\sqrt{2}} = - \sqrt{3}

⇒(α+3)⇒ {\left(\alpha + \sqrt{3}\right)}^{2} = 9 and (β+6)2=16{\left(\beta + \sqrt{6}\right)}^{2} = 16

Hence, (α+3){\left(\alpha + \sqrt{3}\right)}^{2} + {\left(\beta + \sqrt{6}\right)}^{2} = 25

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