Solution 4.1:7c

From Förberedande kurs i matematik 1

By completing the square, we can rewrite the x - and y -terms as quadratic expressions,

x2−2x=x−12−12 

y2+6y=y+32−32 

and the whole equation then has standard form,

x−12−1+y+32−9=−3x−12+y+32=7

From this, we see that the circle has its centre at 1−3  and radius 7 .