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 ? $$|[x-x_0 , y-y_0]|^2 = r^2$$