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The points of intersection of the line ax + by = 0, (a ≠ b) and the circle x² + y² - 2x = 0 are A(a, 0) and B(1, β). The image of the circle with AB as a diameter in the line x + y + 2 = 0 is

Concept: Circle and line intersection

Question

The points of intersection of the line ax + by = 0, (a ≠ b) and the circle x² + y² - 2x = 0 are A(a, 0) and B(1, β). The image of the circle with AB as a diameter in the line x + y + 2 = 0 is
(A) x² + y² + 5x + 5y + 12 = 0
(B) x² + y² + 3x + 5y + 8 = 0
x2+y2+2gx+2fy+c=0x^2+y^2+2gx+2fy+c=0

Try it yourself first

Hint: Start by using the fact that points A and B lie on the given circle to find the values of 'a' and 'β'.

Step-by-step solution

  1. 1

    Find a and β

    A(a,0) on circle • a² + 0² - 2a = 0 • a(a-2) = 0 → a=2 (a≠0)
    a2−2a=0a^2 - 2a = 0
  2. 2

    Find β

    B(1,β) on circle • 1² + β² - 2(1) = 0 • β² - 1 = 0 → β = ±1
    1+β2−2=01 + \beta^2 - 2 = 0
  3. 3

    Determine b and β

    A(a,0) on x²+y²-2x=0 • a²-2a=0 → a=0 or a=2 • B(1,β) on x²+y²-2x=0
  4. 4

    Circle with AB as diameter

    A(2,0), B(1,1) • Center C = ((2+1)/2, (0+1)/2) = (3/2, 1/2) • Radius² = ((2-1)² + (0-1)²)/4 = (1+1)/4 = 2/4 = 1/2
    (x−x1)(x−x2)+(y−y1)(y−y2)=0(x-x_1)(x-x_2)+(y-y_1)(y-y_2)=0
  5. 5

    Image of the circle

    Center C(3/2, 1/2) • Line L: x+y+2=0 • Image C'(x',y')
    x′−x1A=y′−y1B=−2(Ax1+By1+C)A2+B2\frac{x'-x_1}{A} = \frac{y'-y_1}{B} = \frac{-2(Ax_1+By_1+C)}{A^2+B^2}

Final answer

(A) x² + y² + 5x + 5y + 12 = 0

Remember: Reflection of a circle means reflecting its center, radius remains unchanged.

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If a circle passes through the origin and has its center on the x-axis, which of the following can be its equation?

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