a^2+2ab+2ac+4bc=a^2+b^2+c^2+2ab+2ac+2bc-b^2-c^2+2bc=(a+b+c)^2-(b^2-2bc+c^2)=(a+b+c)^2-(b-c)^2=12∴(a+b+c)^2=12+(b-c)^2>=12【当b=c时取等号】∴a+b+c>=√12=2√3即当b=c时,a+b+c能取到最小值2√3...