Standard form of a circle is: (x - h)² + (y - k)² = r² ; where (h,k) is the vertex and r is the radius.
for this example: h = 0, k = 0, and r = 2
(x - 0)² + (y - 0)² = 2² → x² + y² = 4
General form of ANY equation is when everything is one side and 0 is on the other. So, subtract 4 from both sides to get the general equation.
x² + y² - 4 = 0
Answer: x² + y² = 4 (standard form) , x² + y² - 4 = 0 (general form)
