A:m/9
B:9m
C:2m
D:m/2
this ____ t h a s t h i s s
(2015•德州)已知抛物线y=﹣mx2+4x+2m与x轴交于点A(α,0),B(β,0),且1α+1β=﹣2,
设函数f(x)=cos(3x+φ)(0<φ<π),若f(x)+f′(x)是偶函数,则φ=____