设√a=x,√b=y,√c=z原式即可化为 x³+y³+z³≥x²y+y²z+z²x,且x≥0,y≥0,z≥0,∵ x²-2xy+y²≥0∴ x²-xy+y²≥xy∵ x+y≥0∴ (x+y)(x²-xy+y²)≥xy(x+y)即 ...