I want to find the equation but use vector length notation and I'm not sure about how to write it. $ a) r = 2, A(-1; 1)$
the line I'm not sure - $|[x-x_0 , y-y_0]|^2 = r^2$ then I do $(x+1)^2 + (y-1)^2 = 4$
Then for B) , the same thing but for a sphere $ b) r = 9, A(3;-2;-1) $
the line I'm not sure - $|[x-x_0 , y-y_0, z-z0]|^2 = r^2$ then I do $(x-3)^2 + (y+2)^2 + (z+1)^2 = 81$
Is this the right way to do it ? $|[x-x_0 , y-y_0]|^2 = r^2$