Multiple Choice Question (MCQ)

The equation of a circle in the xy-plane is shown here:

x^2 + y^2 + 6x – 4y = –9

What is the radius of the circle?

  1. ×

    1

  2. 2


  3. ×

    3

  4. ×

    4

Collected in the board: Coordinate geometry

Steven Zheng posted 11 months ago


Answer

  1. Convert the equation to the standard circle equation

    (x – h)^2 + (y – k)^2 = r^2

    in which r is the radius of the circle.

    x^2+y^2+6x-4y=-9

    x^2+6x+9+y^2-4y+2=-9+9+4

    (x+3)^2+(y-2)^2=2^2

    Therefore the radius of the circle is 2

    B is correct choice


Steven Zheng posted 2 weeks ago

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