爸爸妈妈上个月收入2548元,支出1857元,结余____.
如图,两个反比例函数y=1x和y=﹣2x的图象分别是l1和l2.设点P在l1上,PC⊥x轴,垂足为C,交l2于点A,PD⊥y轴,垂足为D,交l2于点B,则△PAB的面积为 ____ .
—We mainly ________ buyers from Europe and our products are well received.
下列有关化学用语或叙述正确的是( )