已知函数y=2cos(4x-6/π),则当x=_时，函数取最小值为_。

y=2cos(4x-π/6)
4x-π/6 = 2kπ -π/2
4x =2kπ -π/3
x=(2kπ -π/3)/4 ; k=0,±1,±2,....