CIE A Level Maths: Pure 1复习笔记2.2.2 Finding the Centre & Radius

How can I find the centre and radius from any form of the equation of a circle?

• A circle equation in a different form can always be rearranged into (x- a)² + (y - b)² = r² form in order to find the centre and radius
• This will often involve completing the square