If a circle passes through the point (a, b) and cuts the circle ${x^2}\, + \,{y^2} = 4$ orthogonally, then the locus of its centre is :
$2ax\, - 2by\, - ({a^2}\, + \,{b^2} + 4) = 0$
$2ax\, + 2by\, - ({a^2}\, + \,{b^2} + 4) = 0$
$2ax\, - 2by\, + ({a^2}\, + \,{b^2} + 4) = 0$
$2ax\, + 2by\, + ({a^2}\, + \,{b^2} + 4) = 0$
