Question

【題目】若a是有理數(shù)，則下列各數(shù)一定為正數(shù)的有___．①a；②a+1；③|a+1|；④|a|+1；⑤a2；⑥a2+1；⑦（﹣a）2+1；⑧a3．

Answer 1

【答案】④⑥⑦．

【解析】

根據(jù)平方數(shù)和絕對(duì)值一定為非負(fù)數(shù)對(duì)各小題分析判斷即可得解．

解：①a是任意有理數(shù)；②a+1是任意有理數(shù)；③|a+1|≥0；④|a|+1≥1；⑤a2≥0；⑥a2+1≥1；⑦（﹣a）2+1≥1；⑧a3是任意有理數(shù)，

故答案為：④⑥⑦．