分析:利用相反數(shù)、絕對(duì)值和倒數(shù)的性質(zhì),求解即可.
解答:解:2.5的相反數(shù)是-2.5,互為相反數(shù)的兩個(gè)數(shù)和為0;-
的倒數(shù)是-3,互為倒數(shù)的兩個(gè)數(shù)積為1;絕對(duì)值為3的數(shù)是±3,一個(gè)正數(shù)的絕對(duì)值是它本身,一個(gè)負(fù)數(shù)的絕對(duì)值是它的相反數(shù).
點(diǎn)評(píng):此題考查了相反數(shù)、絕對(duì)值和倒數(shù)的性質(zhì),要求掌握相反數(shù)、絕對(duì)值和倒數(shù)的性質(zhì)及其定義,并能熟練運(yùn)用到實(shí)際當(dāng)中.
絕對(duì)值規(guī)律總結(jié):一個(gè)正數(shù)的絕對(duì)值是它本身;一個(gè)負(fù)數(shù)的絕對(duì)值是它的相反數(shù);0的絕對(duì)值是0.
倒數(shù)的定義:若兩個(gè)數(shù)的乘積是1,我們就稱這兩個(gè)數(shù)互為倒數(shù).
相反數(shù)的定義:只有符號(hào)不同的兩個(gè)數(shù)互為相反數(shù),0的相反數(shù)是0;