7. Find the radius of the circle whose equation is (A) 1 (B) 2 (C) 3 (D) 4 (E) 5

To find the radius of a circle from its equation, we can refer to the standard form of a circle's equation: \((x - h)^2 + (y - k)^2 = r^2\), where \((h, k)\) is the center and \(r\) is the radius. If you have the circle's equation, you would identify \(r^2\) and take the square root to find \(r\). When solving similar problems, a common mistake is not converting back to determine the actual radius from \(r^2\). Keep in mind to check if the equation is already in the standard form or if you need to manipulate it into that format before determining the radius.