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Question: Answered & Verified by Expert
Let C:x2+y2=4 and C':x2+y24λx+9=0 be two circles. If the set of all values of λ so that the circles C and C' intersect at two distinct points, is Ra,b, then the point 8a+12,16b20 lies on the curve:
MathematicsCircleJEE MainJEE Main 2024 (01 Feb Shift 1)
Options:
  • A x2+2y25x+6y=3
  • B 5x2y=11
  • C x24y2=7
  • D 6x2+y2=42
Solution:
1891 Upvotes Verified Answer
The correct answer is: 6x2+y2=42

Given: x2+y2=4

So, centre and radius of C are 0,0 and r1=2 respectively.

Also, C':x2+y24λx+9=0

So, centre and radius of C' are 2λ,0 and r2=4λ29 respectively.

r1r2<CC'<r1+r2

24λ29<2λ<2+4λ29

4+4λ2944λ29<4λ2

λR   ...i

Also, 4λ2<4+4λ29+44λ29

5<44λ29 λ294λ,3232,

2516<4λ29

16964<λ2

16964<λ2

λ,138138,   ...ii

Using i and ii,

λ,138138,

λR138,138

As per question a=138 and b=138

 required point is 8a+12, 16b-20-1, 6 with satisfies option (d).

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