(1)初等解法：f(x)=2*x^2/(x-3)先对分子进行配方：2*x^2=2*[(x-3)^2+6x-9]=2*[(x-3)^2+6(x-3)+9]f(x)=2*x^2/(x-3)=2*[(x-3)^2+6(x-3)+9]/(x-3)=2(x-3)+12+18/(x-3)=2(x-3)+18/(x-3)+12>=2*√[2(x-3)*18/(x-3)]+12 {...