划一公式：Asinx+Bcosx=√（A^2+B^2）sin（x+φ）【tanφ=B/A】
y=-acos2x-√3 asin2x+2a+b
y=-(√3asin2x+acos2x)+2a+b
y=-2asin(2x+π/6)+2a+b,x属于[0,π/2]
值域为[5,1]
增区间：2kπ-π/2<=2x+π/6<=2kπ+π/2
kπ-π/3<=x<=kπ+π/6
函数在[0,π/6]为增函数
在[π/6,π/2]为减函数
ymax=f(π/6)=-2asin(2x+π/6)+2a+b=5,==>b=5
将b=5带入
ymin=f(π/2)=-2asin(2x+π/6)+2a+b=1
-√3a+2a+5=1
(2-√3)a=-4
a=-4/(2-√3)=-8-4√3
所以：a=-8-4√3
b=5