Question

Find the equation of the circle with centre $(-1,-1)$ and radius $3$

Answer 1

Since the centre of the circle is $(-1,-1)$ and its radius $3$

$\therefore ,$ the equation of the circle is ${(x-(-1))}^2+{(y-(-1))}^2=3^2$

$\Rightarrow {(x+1)}^2+{(y+1)}^2=9$

$\Rightarrow x^2+2x+1+y^2+2y+1-9=0$

$\Rightarrow x^2+y^2+2x+2y-7=0$