__________ of students are in the room and nine ________ of them are girls.
若|x2﹣16|+ y−3 =0,则x+y=____.
设向量a→=(1,﹣2),b→=(﹣3,2),若表示向量3a→,2b→﹣a→,c→的有向线段首尾相接能构成三角形,则a→⋅c→=( )