It is important us each other?
A:with; to help
B:with; help
C:for; to help
D:for; help
设向量a→=(x,1),b→=(4,x),若a→,b→方向相反,则实数x的值是( )
What's the weather?
如图,点D、E分别在AB、BC上,DE∥AC,AF∥BC,∠1=70°,则∠2=____°.