由f(x+2)=3f(x)
得f(x+4)=3f(x+2)=9f(x)
f(x)=(1/9)f(x+4)
设x∈[-4,-2],则x+4∈[0,2]
故f(x)=(1/9)f(x+4)=(1/9)[(x+4)^2-2(x+4)]
=(1/9)(x+3)^2-1/9
所以当x=-3时,f(x)取得最小值-1/9
由f(x+2)=3f(x)
得f(x+4)=3f(x+2)=9f(x)
f(x)=(1/9)f(x+4)
设x∈[-4,-2],则x+4∈[0,2]
故f(x)=(1/9)f(x+4)=(1/9)[(x+4)^2-2(x+4)]
=(1/9)(x+3)^2-1/9
所以当x=-3时,f(x)取得最小值-1/9