求函数y=3-4cos(2x+ π/3),x∈[-π/3,π/6]的最大值,最小值及相应的x值

y=3-4cos(2x+ π/3),∵x∈[-π/3,π/6]∴2x∈[-2π/3,π/3]∴2x+ π/3∈[-π/3,2π/3]当2x+ π/3=0,即x=-π/6时,cos(2x+ π/3)=-1,y取得最小值-1当2x+ π/3=2π/3,即x=π/6时,cos(2x+ π/3)=-1/2,y取得最大值5