变形为
y=-2asin(2x+π/6)+a+b
2x+π/6∈[π/6,7π/6]
(1)当a>0时
2x+π/6=π/2时,y有最小值=b-a=-5
2x+π/6=7π/6时,y有最大值=2a+b=1
得a=2,b=-3
(2)当a<0时
2x+π/6=π/2时,y有最大值=b-a=1
2x+π/6=7π/6时,y有最小值=2a+b=-5
得a=-2,b=-1