已知向量 a→ , b→ 满足| a→ |=1,| b→ |= 3 ,|2 a→ + b→ |= 7 ,则 b→ 与 a→ ﹣ b→ 的夹角为( )
若函数fx=sinωxω>0在区间0,π3上单调递增,在区间π3,π2上单调递减,则ω=( )
— Alice, could you help me ________ the meat? I want to make some dumplings for dinner.
— OK. I'll do it right away.