Question

What is the general form of the equation of a circle with its center at (-2,1) and passing though (-4,1) ?

Answer 1

Equation is :( x + 2 )² + ( y - 1 )² = r²( - 4 + 2 )² + ( 1 - 1 )² = r²4 = r², than we will plug in to a formula:( x + 2 )² + ( y - 1 )² = 4x² + 4 x + 4 + y² - 2 y +1 = 4x² + y² + 4 x - 2 y + 1 = 0
the answer is : x2 + y2 + 4x − 2y + 1 = 0