∵(a²+b²+c²)(x²+y²+z²)=a²x²+b²y²+c²z²+a²y²+a²z²+b²x²+b²z²+c²x²+c²y²(ax+by+cz)
...我们老师说可以先变为4(a²+b²+c²)(x²+y²+z²)≥(2ax+2by+2cz)²来解，我看着很像b²-4ac就不知道怎么解，求教···谢了·············谢了··········