The equation of the circle concentric with the circle x2 + y2 - 6

Subject

Mathematics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

11.

  • - 8, 152

  • 8, - 152

  • - 8, - 152


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12.

The equation of the circle concentric with the circle x2 + y2 - 6x + 12y + 15 = 0 and of double its area is

  • x2 + y2 - 6x +12y - 15 = 0

  • x2 + y2 - 6x +12y - 30 = 0

  • x2 + y2 - 6x +12y - 25 = 0

  • x2 + y2 - 6x +12y - 20 = 0


A.

x2 + y2 - 6x +12y - 15 = 0

The equation of the circle is S = x2 + y2 - 6x + 12y + 15 = 0Let the equation of concentric circle of given circles isS2 = x2 + y2 - 6x + 12y + 15 = 0On comparing the circle S1 with,x2 + y2 + 2gx + 2fy + c = 0 g = - 3, f = 6, c = 15Then, radius of circle is = g2 + f2 - c= 9 + 36 - 15= 45 - 15= 30 unitsand centre is - g, - f = 3, - 6Now, te area of the circle S is = πradius2                                               = π302                                               = 30πLet the radius of the concentric cirlce is r2r2 = g2 + f2 - c    = 9 + 36 - c    = 45 - cThen, according to question, the area of concentric circle = 2 × area of S= 2 × 30π = 60π πr22 = 60π 45 - c2 = 60         45 - c = 60                   c = - 15Hence, the equation of concentric circle isx2 + y2  + 2- 3x + 26y + - 15 = 0x2 + y2 - 6x + 12y - 15 = 0


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13.

If the circle x2 + y2 + 2x + 3y + 1 = 0 cuts another circle x2 + y+ 4x + 3y + 2 = 0 in A and B, then the equation of the circle with AB as a diameter is

  • x2 + y2  + x + 3y + 1 = 0

  • 2x2 + 2y2  + 2x + 6y + 1 = 0

  • x2 + y2  + x + 6y + 1 = 0

  • 2x2 + 2y2  + x + 3y + 1 = 0


14.

The equation of the hyperbola which passes through the point (2, 3) and has the asymptotes 4x + 3y - 7 = 0 and x - 2y - 1 = 0 is

  • 4x2 + 5xy - 6y2 - 11x + 11y + 50 = 0

  • 4x2 + 5xy - 6y2 - 11x + 11y - 43 = 0

  • 4x2 - 5xy - 6y2 - 11x + 11y + 57 = 0

  • x2 - 5xy - y2 - 11x + 11y - 43 = 0


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15.

The product of the perpendicular distances from any point on the hyperbola x2a2 - y2b2 = 1 to its asymtotes is

  • a2b2a2 - b2

  • a2b2a2 + b2

  • a2 + b2a2b2

  • a2 - b2a2b2


16.

If the lines 2x + 3y +12 = 0, x - yy + k = 0 are conjugate with respect to the parabola y2 = 8x, then k is equal to

  • 10

  • 72

  • - 12

  • - 2


17.

Find the equation to the parabola, whose axis parallel to they-axis and which passes through the points (0, 4), (1, 9) and (4, 5) is

  • y = - x+ x + 4

  • y = - x+ x + 1

  • y = - 1912x2 + 7912x + 4

  • y = - 1912x2 + 8912x + 4


18.

If ∝, ß, y are the roots of the equation x3 - 6x2 + 11x - 6 = 0 and if a = ∝2 + ß2 + γ2, b = ∝ß + ßγ + γ∝ and  c = (∝ + ß)(ß + γ)(γ + ∝), then the correct inequality among the following is

  • a < b < c

  • b < a < c

  • b < c < a

  • c < a < b


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19.

A plane meets the coordinate axes at A, B, C so that the centroid of the triangle ABC is (1, 2, 4). Then, the equation of the plane is

  • x + 2y +4z =12

  • 4x + 2y + z = 12

  • x + 2y + 4z = 3

  • 4x + 2y + z = 3


20.

If (2, 3, - 3) is one end of a diameter of the sphere x2 + y+ z- 6x - 12y - 2z + 20 = 0, then the other end of the diameter is

  • (4, 9, - 1)

  • (4, 9, 5)

  • (- 8, - 15, 1)

  • (8, 15, 5)


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