Hello,
Middle[AB]=(-11/2,9/2)
slope AB=(5-4)/(-4+7)=1/3
slope mediatrice=-3
Mediatrice [AB]: y-9/2=-3(x+11/2)==>3x+y=-12 (1)
Middle[BC]=(-2,4)
slope BC=(3-5)/(0+4)=-1/2
slope mediatrice = 2
Mediatrice [BC]: y-4=2(x+2)===>2x-y=-8 (2)
(1)+(2)==>5x=-20==>x=-4
y=2*(4)+8==>y=0
Center (-4,0)
