有理数的乘除混合运算VIP免费

１.5有理数的乘除（第3课时）)2(0)4()3()9)(3()(3)2(4)3)(1(31一、巩固旧知一、巩固旧知4575.085751257)53()2512)(6()8()48)(5(—）（）—（）—（二例题示范，初步运用例3计算：2-5-25-1）（1-2-51-25-2-5-25-1解56-4-6-2）（45-65-41-6-56-4-6-2）解：（例4计算：45-52-54-51431）（12141-4345-52-45-514345-52-54-51431解：2-352.0-15-2）（316-31-5-21-325-2-31-15-2-352.0-15-2）解：（有理数乘、除的混合运算，可统一化为乘法运算。含加、减、乘、除的算式，如没有括号，应先做乘除运算，后做加减运算；如有括号，应先做括号里的运算。•乘法运算律：•1、乘法交换律：ab=ba•2、乘法结合律：(ab)c=a(bc)•3、分配率：a(b+c)=ab+ac•运用这些规律，有时可以简化计算。例5计算：12-21-61411）（162312211261124112216141)1(:解（分配律）1001.01001.02）（110001.0101.01001.01001.01001.01001.02）解：（（乘法符号法则）（乘法交换律、结合律）5615810156.451131324332113.325.053321.245532512.1三、拓展提高，形成能力四、回顾小结，突出重点习题1.5第5、6题