a^2+b^2+c^2-ab-3b-2c+4=0,则a+b+c=?

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 a=b/2,b/2=1,c=1 a=1,b=2,c=1 所以a+b+c=1+2+1=4