2018_2019学年七年级数学上册第二章有理数及其运算2.7有理数的乘法（第2课时）课件（新版）北师大版.ppt

第二课时,1.乘法的交换律:ab= ; 乘法的结合律:(ab)c= ; 乘法对加法的分配律:a(b+c)= . 2.填空:3(-5)= 3=-15; (-13.35)0.2=-13.3(5 )=-13.3;,ba,a(bc),ab+ac,-5,0.2,(-15),1,2,3,4,答案,1,2,3,4,答案,1,2,3,4,答案,3.(1)在算式(-25)(-4)(-0.77)=(-25)(-4)(-0.77)中,应用了律; (2)在算式3.4(-98)=3.4(2-100)=3.42-3.4100中,应用了律.,1,2,3,4,答案,4.运用简便方法计算: (1)0.125(-7)8;,