x∈[0,π/2]
2x∈[0,π]
2x+π/6∈[π/6,7π/6]
sin(2x+π/6)∈[-1/2,1]
-2asin(2x+π/6)∈[-2a,a]
-2asin(2x+π/6)+2a+b∈[b,3a+b]
又f(x)值域是[-5,1]
所以b=-5,3a+b=1
所以a=2,b=-5
x∈[0,π/2]
2x∈[0,π]
2x+π/6∈[π/6,7π/6]
sin(2x+π/6)∈[-1/2,1]
-2asin(2x+π/6)∈[-2a,a]
-2asin(2x+π/6)+2a+b∈[b,3a+b]
又f(x)值域是[-5,1]
所以b=-5,3a+b=1
所以a=2,b=-5