first find equation center is (h,k) then (x-h)^2+(y-k)^2=r^2 given (7,0) is center (x-7)^2+y^2=r^2 also given (2,0) (2-7)^2+0^2=r^2 (-5)^2=r^2 25=r^2
(x-7)^2+y^2=25 is equation
take derivitive of both sides, implicit differntiaton 2(x-7)+2y dy/dx=0 2(x-7)=-2y dy/dx (7-x)/y=dy/dx at (2,0) (7-2)/0 undefined that means the line is x=something (2,0) the equation is x=2
