Q39 / 90 · JEE Main 2024 (01 Feb Shift 1) · Mathematics

Let C:x2+y2=4 and C':x2+y2−4λx+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 R−a,b, then the point 8a+12,16b−20 lies on the curve:

  • A
    x2+2y2−5x+6y=3
  • B
    5x2−y=−11
  • C
    x2−4y2=7
  • Correct answer
    D
    6x2+y2=42

Solution

Given: x2+y2=4

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

Also, C':x2+y2−4λx+9=0

So, centre and radius of C' are 2λ,0 and r2=4λ2−9 respectively.

⇒r1−r2<CC'<r1+r2

⇒2−4λ2−9<2λ<2+4λ2−9

⇒4+4λ2−9−44λ2−9<4λ2

⇒λ∈R   ...i

Also, 4λ2<4+4λ2−9+44λ2−9

⇒5<44λ2−9 λ2≥94⇒λ∈−∞,−32∪32,∞

⇒2516<4λ2−9

⇒16964<λ2

⇒16964<λ2

⇒λ∈−∞,−138∪138,∞   ...ii

Using i and ii,

⇒λ∈−∞,−138∪138,∞

⇒λ∈R−−138,138

As per question a=−138 and b=138

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

Hence, the correct answer is option: 'D'.

Relevant Questions