Enter the center coordinates and a positive radius. The calculator then builds both circle equations from first principles.

1. Enter h, k, and r.
2. Check that the radius is positive.
3. Read both the standard and general forms from the result card.

For center (3, -4) and radius 5, the standard form is (x - 3)^2 + (y + 4)^2 = 25.

The equivalent general form is x^2 + y^2 - 6x + 8y = 0.

Negative centers are allowed and are rendered with the correct sign in the standard form.

Blank and malformed inputs are rejected before any equation is produced, so the page cannot silently emit a malformed circle.