函数是y=-3sin(2x-π/6)吧
单调减区间是[Kπ-π/6,Kπ+π/3]
分析：sin(2x）单调增区间是[Kπ-π/4,Kπ+π/4]
sin(2x-π/6)单调增区间是[Kπ-π/6,Kπ+π/3]
-3sin(2x-π/6)单调减区间是[Kπ-π/6,Kπ+π/3]