AQA A Level Maths: Pure复习笔记3.2.2 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