Solution 4.1:6a
From Förberedande kurs i matematik 1
If we write the equation as
\displaystyle (x-0)^2 + (y-0)^2 = 9 |
we can interpret the left-hand side as the square of the distance between the points (x,y) and (0,0). The whole equation says that the distance from a point (x,y) to the origin should be constant and equal to \displaystyle \sqrt{9}=3\,, which describes a circle with its centre at the origin and radius 3.
![Image:4_1_6_a.gif](/wikis/2008/bridgecourse1-ImperialCollege/img_auth.php/4/48/4_1_6_a.gif)