x²-6x+8y+y²+25=0(x²-6x+9)+(y²+8y+16)=0(x-3)²+(y+4)²=0x=3 y=-42x-3y=6+12=18a²+b²+c²=ab+bc+ac2(a² + b² + c²)=2(ab + bc + ac)a² -2ab+ b&su...