一 填空题(每小题4分,共20分):
2232
1.下列各式-1,3,0,(-4),-|-5|,-(+3.2),,0.815的计算结果,是整
422
数的有________________,是分数的有_________________,是正数的有_________________,
是负数的有___________________; 2.a的相反数仍是a,则a=______; 3.a的绝对值仍是-a,则a为______; 4.绝对值不大于2的整数有_______;
5.700000用科学记数法表示是_ __,近似数9.105×104
精确到_ _位,有___有效数字.二 判断正误(每小题3分,共21分):
1.0是非负整数„„„„„„„„„„„„„„„„„„„„„„„„„„„( ) 2.若a>b,则|a|>|b|„„„„„„„„„„„„„„„„„„„„„„„( )
3.23=32
„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„( ) 4.-73=(-7)×(-7)×(-7)„„„„„„„„„„„„„„„„„( )
5.若a是有理数,则a2
>0„„„„„„„„„„„„„„„„„„„„„„( )
6. 若a是整数时,必有an
≥0(n是非0自然数) „„„„„„„„„„„„„„„„( ) 7. 大于-1且小于0的有理数的立方一定大于原数„„„„„„„„„„„„„„( ) 三 选择题(每小题4分,共24分):
1.平方得4的数的是„„„„„„„„„„„„„„„„„„„„„„„„„( ) (A)2 (B)-2 (C)2或-2 (D)不存在
2.下列说法错误的是„„„„„„„„„„„„„„„„„„„„„„„„„( ) (A)数轴的三要素是原点,正方向、单位长度 (B)数轴上的每一个点都表示一个有理数
(C)数轴上右边的点总比左边的点所表示的数大 (D)表示负数的点位于原点左侧
3.下列运算结果属于负数的是„„„„„„„„„„„„„„„„„„„„„( ) (A)-(1-98×7) (B)(1-9)8-17 (C)-(1-98)×7 (D)1-(9×7)(-8)
4.一个数的奇次幂是负数,那么这个数是„„„„„„„„„„„„„„„„( ) (A)正数 (B)负数 (C)非正数 (D)非负数
5.若ab=|ab|,必有„„„„„„„„„„„„„„„„„„„„„„„„( ) (A)ab不小于0 (B)a,b符号不同 (C)ab>0 (D)a<0 ,b<0
6.-
313,-0.2,-0.22三个数之间的大小关系是„„„„„„„„„„„( ) (A)-313>-0.2>-0.22 (B)-313<-0.2<-0.22
(C)-3313>-0.22>-0.2 (D)-0.2>-0.22>-13
四 计算(每小题7分,共28分):
1.(-58)×(-4)2-0.25×(-5)×(-4)3
; 2.-24
÷(-22113)×2+52×(-6)-0.25;
3.
1112(12)0.4; 224(0.2)757)×(-18)+1.95×6-1.45×0.4. 9618 4.(
五 (本题7分)
当a1,b2
2322
时,求代数式3(a+b)-6ab的值. 3
22一、答案:1、-1,0,(-4),-|-5|,;
43,-(+3.2),0.815; 323222
(-4),,0.815;
4232
2
-1,-|-5|,-(+3.2).
2、答案:0.
解析:应从正数、负数和0 三个方面逐一考虑再作判断.结果应为a=0 3、答案:负数或0.
解析:应从正数、负数和0 三个方面逐一考虑再作判断.结果应为负数. 4、答案:0,±1,2.
解析:不大于2的整数包括2,不小于-2的整数包括-2,所以不应丢掉2.
5
5、答案:7×10;十;4个. 解析:
54
700000=7×100000=7×10;9.105×10=9.105×1000=91050,所以是精确到十位;最后的0前的数字5直到左面第一个不是0的数字9,共有4个数字,所以有4个有效数字.
二、1、答案:√
解析:0既是非负数,也是整数. 2、答案:×
解析:不仅考虑正数,也要考虑负数和0 .当a=0,b<0 时,或a<0且b<0时, |a|>|b|都不成立. 3、答案:×
3232
解析:2=2×2×2=8,3=3×3=9,所以23 4、答案:×
解析:-73不能理解为-7×3. 5、答案:×
2
解析:不能忘记0.当a=0时,a≯0. 6、答案:×
3
解析:注意,当a<0时,a的奇次方是负数,如(-3)=-27<0. 7、答案:√ 解析:
大于-1且小于0的有理数的绝对值都是小于1的正数,它们的乘积的绝对值变小;又,大于-1且小于0的有理数的立方一定是负数,所以大于-1且小于0的有理数的立方一定大于原数. 三、1、答案:C.
解析:平方得4的数不仅是2,也不仅是-2,所以答2或-2才完整. 2、答案:B. 解析:
虽然每一个有理数都可以用数轴上唯一的一个点来表示,但是数轴上的每一个点不都表示一个有理数. 3、答案:B. 解析:
负数的相反数是正数,所以(A)和(C)是正数;“减去负数等于加上它的相反数(正数)”所以(D)也是正数;只有(B):(1-9)8-17 =-8×8-17 =-64-17 =-81.可知只有(B)正确.
2
4、答案:B.
解析:正数的奇次幂是正数,0的奇次幂是0,所以(A)、(C)(D)都不正确. 5、答案:A. 解析:
(B)显然不正确;(C)和(D)虽然都能使ab=|ab|成立,但ab=|ab|成立时,(C)和(D)未必成立,所以(C)和(D)都不成立. 6、答案:D. 解析:
比较各绝对值的大小.由于0.2>-0.22>-
33≈0.23,所以有>0.22>0.2,则有-13133. 131. 4四、1、答案:-90.
解析:注意运算顺序,且0.25 = (-
523
)×(-4)-0.25×(-5)×(-4)85
=(-)×16-0.25×(-5)×(-64)
8 =(-5)×2-(-16)×(-5) =-10-80 =-90.
应注意,计算-10-80 时应看作-10 与-80 的和.
2、答案:10
5. 64
解析:注意-2=-2×2×2×2 =-16,再统一为分数计算:
211)×2+5×(-)-0.25 32681111 =-16÷(-)×2+×(-)-
32643113 =-16×(-)×2+(-)-
8121214 = 12+(-)
127 = 12-
665 =.
6 -2÷(-2
4
3、答案:50.
解析:注意统一为真分数再按括号规定的顺序计算:
1112(12)0.4 24(0.2)21925(1) 1245()25552 = 25
2451 = 251
21 = 25
2 =
= 25×2 = 50.
注意分配律的运用. 4、答案:17.12.
解析:注意分配律的运用,可以避免通分. (757)×(-18)+1.95×6-1.45×0.4 9618 = 14-15+7+11.7-0.58
= 6+11.12 = 17.12.
89. 32
解析:3(a+b)-6ab
22222 = 3(12)6(-1)(2)
333313258 = 3(-)-6()()
33316980 = 3×-
9389 = .
3五、答案:
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