配方a^2+b^2+c^2+4-(ab+3b+2c)=0(a^2-ab+b^2/4)+(3b^2/4-3b+3)+(c^2-2c+1)=0(a-b/2)^2+3(b/2-1)^2+(c-1)^2=0平方都大于等于0相加为0则各项均为0a=b/2,b/2=1,c=1a=1,b=2,c=1 a+b+c=4