F（X）=A*B+m
得到F（X）=2cosxcosx+2√3sinxcosx+m=√3sin2x+cos2x+1+m
=2sin（2x+π/6）+1+m
当x属于[-π/6,π/6]时,2x+π/6属于[-π/6,π/2]
得到最大值是f（π/6）,最小值是f（-π/6）
故2+1+m-1+1+m=3
m=0