【導(dǎo)讀】為負(fù)),經(jīng)3天后水位共下降了多少米?得負(fù)并把絕對(duì)值相乘;思考:-2×(-3)=+6?(-4)×(-5)×號(hào)由負(fù)因數(shù)的個(gè)數(shù)決定。數(shù)個(gè)時(shí),積的符號(hào)為正。得原來(lái)那個(gè)數(shù)的相反數(shù)。如果因數(shù)是帶分?jǐn)?shù),應(yīng)先化。成假分?jǐn)?shù),然后相乘。今天的課就到這里,請(qǐng)同學(xué)們按時(shí)完成回家作業(yè)!