推荐回答(3个)
1、计算: (1)-5-9+3; (2)10-17+8; (3)-3-4+19-11; (4)-8+12-16-23. 2.计算: (1)-4.2+5.7-8.4+10; (2)6.1-3.7-4.9+1.8; 3.计算: (1)(—36)—(—25)—(+36)+(+72); (2)(—8)—(—3)+(+5)—(+9); (3) ; (4)—9+(—3 )+3 ; 4.计算: (1) 12-(-18)+(-7)-15; (2) -40-28-(-19)+(-24)-(-32); (3)4.7-(-8.9)-7.5+(-6); 有理数的混合运算 1.计算(五分钟练习): (5)-252; (6)(-2)3;(7)-7+3-6; (8)(-3)×(-8)×25; (13)(-616)÷(-28); (14)-100-27; (15)(-1)101; (16)021; (17)(-2)4; (18)(-4)2; (19)-32; (20)-23; (24)3.4×104÷(-5). . 课堂练习 计算:(1)-2.5×(-4.8)×(0.09)÷(-0.27); 例3 计算: (1)(-3)×(-5)2; (2)〔(-3)×(-5)〕2; (3)(-3)2-(-6); (4)(-4×32)-(-4×3)2. 审题:运算顺序如何? 解:(1)(-3)×(-5)2=(-3)×25=-75. (2)〔(-3)×(-5)〕2=(15)2=225. (3)(-3)2-(-6)=9-(-6)=9+6=15. (4)(-4×32)-(-4×3)2 =(-4×9)-(-12)2 =-36-144 =-180. 注意:搞清(1),(2)的运算顺序,(1)中先乘方,再相乘,(2)中先计算括号内的,然后再乘方.(3)中先乘方,再相减,(4)中的运算顺序要分清,第一项(-4×32)里,先乘方再相乘,第二项(-4×3)2中,小括号里先相乘,再乘方,最后相减. 课堂练习 计算: (1)-72; (2)(-7)2; (3)-(-7)2; (7)(-8÷23)-(-8÷2)3. 例4 计算 (-2)2-(-52)×(-1)5+87÷(-3)×(-1)4. 审题:(1)存在哪几级运算? (2)运算顺序如何确定? 解: (-2)2-(-52)×(-1)5+87÷(-3)×(-1)4 =4-(-25)×(-1)+87÷(-3)×1(先乘方) =4-25-29(再乘除) =-50.(最后相加) 注意:(-2)2=4,-52=-25,(-1)5=-1,(-1)4=1. 课堂练习 计算: (1)-9+5×(-6)-(-4)2÷(-8); (2)2×(-3)3-4×(-3)+15. 3.在带有括号的运算中,先算小括号,再算中括号,最后算大括号. 课堂练习 计算: 三、小结 教师引导学生一起总结有理数混合运算的规律. 1.先乘方,再乘除,最后加减; 2.同级运算从左到右按顺序运算; 3.若有括号,先小再中最后大,依次计算. 四、作业 1.计算: 2.计算: (1)-8+4÷(-2); (2)6-(-12)÷(-3); (3)3•(-4)+(-28)÷7; (4)(-7)(-5)-90÷(-15); 3.计算: 4.计算: (7)1÷(-1)+0÷4-(-4)(-1);(8)18+32÷(-2)3-(-4)2×5. 5*.计算(题中的字母均为自然数): (1)(-12)2÷(-4)3-2×(-1)2n-1; (4)〔(-2)4+(-4)2•(-1)7〕2m•(53+35). 第二份 初一数学测试(六) (第一章 有理数 2001、10、18) 命题人:孙朝仁 得分 一、 选择题:(每题3分,共30分) 1.|-5|等于………………………………………………………………( ) (A)-5 (B)5 (C)±5 (D)0.2 2.在数轴上原点及原点右边的点所表示的数是……………………( ) (A)正数 (B)负数 (C)非正数 (D)非负数 3.用代数式表示“ 、b两数积与m的差”是………………………( ) (A) (B) (C) (D) 4.倒数等于它本身的数有………………………………………………( ) (A)1个 (B)2个 (C)3个 (D)无数个 5.在 (n是正整数)这六数中,负数的个数是……………………………………………………………………( ) (A)1个 (B)2个 (C)3个 (D)4个 6.若数轴上的点A、B分别与有理数a、b对应,则下列关系正确的是( ) (A)a<b (B)-a<b (C)|a|<|b| (D)-a>-b • • • 7.若|a-2|=2-a,则数a在数轴上的对应点在 (A) 表示数2的点的左侧 (B)表示数2的点的右侧……………( ) (C) 表示数2的点或表示数2的点的左侧 (D)表示数2的点或表示数2的点的左侧 8.计算 的结果是……………………………( ) (A) (B) (C) (D) 9.下列说法正确的是…………………………………………………………( ) (A) 有理数就是正有理数和负有理数(B)最小的有理数是0 (C)有理数都可以在数轴上找到表示它的一个点(D)整数不能写成分数形式 10.下列说法中错误的是………………………………………………………( ) (A) 任何正整数都是由若干个“1”组成 (B) 在自然数集中,总可以进行的运算是加法、减法、乘法 (C) 任意一个自然数m加上正整数n等于m进行n次加1运算 (D)分数 的特征性质是它与数m的乘积正好等于n 二、 填空题:(每题4分,共32分) 11.-0.2的相反数是 ,倒数是 。 12.冰箱冷藏室的温度是3℃,冷冻室的温度比冷藏室的温度低15℃,则冷冻室温度是 ℃。 13.紧接在奇数a后面的三个偶数是 。 14.绝对值不大于4的负整数是 。 15.计算: = 。 16.若a<0
题目很有趣味性,有双向选择,不认真做题,容易出错,100道太多了不好回答,举个例子,计算=,2一1=3一2,不知道做100道能得多少分不知道,但是题目有很思考空间,让人觉得自己是井底之蛙,原来还是有许多高人比自己强一百倍。
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