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Circles

SAT Math· difficulty 4/5

A circle is given by x2+y2−8x+6y=0x^2 + y^2 - 8x + 6y = 0. What are its center and radius?

  • A

    Center (4,−3)(4, -3), radius 55

    check_circle
  • B

    Center (4,−3)(4, -3), radius 2525

  • C

    Center (−4,3)(-4, 3), radius 55

  • D

    Center (8,−6)(8, -6), radius 1010

Explanation

Complete the square: (x−4)2−16+(y+3)2−9=0(x-4)^2 - 16 + (y+3)^2 - 9 = 0, so (x−4)2+(y+3)2=25(x-4)^2 + (y+3)^2 = 25. Center (4,−3)(4, -3), radius 55.

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