题目列表(包括答案和解析)
21. 解:原式=…………………………2分
===………………5分
20. 解:
取和2以外的任何数
19. 解:原式= ==.
当,时,原式=
18. 解:设该厂原来每天生产顶帐篷
据题意得:
解这个方程得
经检验是原分式方程的解
答:该厂原来每天生产100顶帐篷.
17. 解:设该文具厂原来每天加工这种文具套.
根据题意,列方程得,
解得
经检验,是原方程的根.
答:该文具厂原来每天加工这种文具100套.
16. 解:设y=,则原方程可化为y-=-1, ∴ ∴=3,=-4当=3时, =3 ∴-3=0∴=-1,=3;当=-4时, =-4∴+4=0无解,经检验使原方程有意义∴原方程的解为=-1,=3
15. 化简得原式=,代入得=
14. 解:(1)设乙队单独完成这项工程需要x天,则甲队单独完成这项工程需要天.
根据题意,得
解得x=90.
经检验,x=90是原方程的根. ……3分
∴
答:甲、乙两队单独完成这项工程需要60天和90天. ……1分
(2)设甲、乙两队合作完成这项工程需要y天,则有
解得y=36. ……2分
需要施工费用:36×(0.84+0.56)=50.4(万元). ……1分
∵50.4>50,
∴工程预算的施工费用不够用,需追加预算0.4万元. ……1分
13. 解:原式=2x-1+ ……4分
=2x-1+x+2
=3x+1 ……2分
12. 解:聪聪说的有理.······························································································· 1分
················································································ 3分
··················································································································· 4分
······························································································································· 5分
只要使原式有意义,无论取何值,原式的值都相同,为常数1.····························· 6分
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