Question

Find the equation of centre $(1,1)$ and radius $\sqrt{2}$.

Answer 1

centre (1,1) (p,a)

radius $\sqrt{2}$=r

$(x-p{)}^2+(y-q{)}^2=r^2$

$\Rightarrow (x-1{)}^2+(y-1{)}^2=(\sqrt{2}{)}^2$

$\Rightarrow x^2+1+2x+y^2+1+2y=2$

$\Rightarrow x^2+y^2+2x+2y=0$