Verified answer

Completing the square to get the equation into the form of (x - h)² + (y - k)² = r² gives:

x² + y² - 250y = 0

==> x² + (y² - 250y) = 0

==> x² + (y² - 250 + 125²) = 125²

==> x² + (y - 125)² = 125²

Since the radius of a circle with the equation:

(x - h)² + (y - k)² = r²

is r, the equation we have gives radius as 125 units and so the diameter is 125*2 = 250 units.

I hope that helps!

You need to complete the square in order to find the radius. Which you would then just multiply by two to find the diameter.