5x²-12xy+10y²-6x-4y+13=0(x²-6x+9)+(y²-4y+4)+(4x²-12xy+9y²)=0(x-3)²+(y-2)²+(2x-3y)²=0平方项恒非负,三个平方项之和=0,三个平方项分别=0x-3=0y-2=02x-3y=0解得x=3 ...