(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 {因x>3,x-3>0}
=2*√36+12
=24
(2)高等解法：
对f(x)=2*x^2/(x-3)求导数f'(x)并令f'(x)=0
=>f'(x)=[4x(x-3)-2x^2]/(x-3)^2=0
=>x=0（舍去,因x>3）x=6
将x=6带入f(x)得到：
f(6)=2*6^2/(6-3)=24