Answer:
Explanation:
The error was in Step 2. The student attempted to "complete the square" by adding 4 to x^2 + 4x and then subtracting 4 from the other side of the equation.
The work, if done correctly, would look like this:
x^2 + 4x + 4 - 4 = -y^2 + 20.
This condenses to:
(x + 2)^2 - 4 + y^2 = 20
(x + 2)^2 + y^2 = 24
This circle has its center at (-2, 0) and its radius is √24 = √4√6, or 2√6