randRange(-9, 9) randRange(-9, 9) randRange(1, 7) H === 0 ? "x^2" : expr(["^", ["+", "x", -H], 2]) K === 0 ? "y^2" : expr(["^", ["+", "y", -K], 2])

The equation of a circle C is expr(["+", X2T, Y2T]) = R * R.

What are its center (h, k) and its radius r?

(h, k) = (H, K)

r = R

The equation of a circle with center (h, k) and radius r is (x - h)^2 + (y - k)^2 = r^2.

We can rewrite the given equation as (x - negParens(H))^2 + (y - negParens(K))^2 = R^2.

Thus, (h, k) = (H, K) and r = R.