6) What is the radius of a circle with the equation x2 + y2 – 14x + 10y = 250?

4 Answers

• assuming you mean x^2 + y^2 − 14x + 10y = 250

  ∴ x^2 − 14x + y^2 + 10y = 250

  ∴ x^2 − 14x + (-14/2)^2 + y^2 + 10y + (10/2)^2 = 250 + (-14/2)^2 + (10/2)^2

  ∴ (x − 7)^2 + (y + 5)^2 = 324

  ∴ (x − 7)^2 + (y + 5)^2 = 18^2

  the radius is 18 units

• You need to complete the square in order to do this..

  x^2 + y^2 -14x + 10y = 250

  Completing the square gives you

  (x-7)^2 + (y+5)^2 = 324

  Since the equation of a circle gives you r^2 you just take the square root

  sqrt(324) = 18

  So the answer is D

• r^2=250-49-25=..

• d