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1、对数对数的的运运算性算性质质 数学组 陈育峰一、复习回顾:对数的定义:如果如果 ab=N (a0,a1),),那么数那么数b叫做以叫做以a为底为底N的的对数对数,记作,记作 b=logaN对数的性质:NaaNaaalog)3(01log21log1)()(二、对数的运算性质证明:MnnpMaaMMapMNMNMqpNMaaaNMNaMaqNpMananpnpnpaaaaaqpqpqpaaloglog)(,log3loglogloglog,.,log,log)2,则)设则设三、对数的运算性质的应用例4、若a0,a1,x0,y0,且xy,下列式子中正确的个数( ) A.0个 B. 1个 C. 2个
2、 D. 3个 例5、计算: yxyxyxyxyxyxyxyxaaaaaaaaaaaloglog)(log4logloglog3)log(loglog2)(logloglog1),),)20lg5lg44log36log)3(100lg)2();39(log13351523)()(2100lg)205lg(20lg5lg)4(29log436log4log36log3529542513log53log10lg51100lg)2(3log9log)39(log133333432515323523)()解:(zyxzyxzyxzyxzyxzyxyzxyzxzyxyzxaaaaaaaaaaaaaaaa
3、aaaaaaloglog2log21)(logloglog) 3(logloglog2)log(loglog2logloglog2)(logloglog)2(logloglog)(log1222222)解:(zyxyzxyzxzyxaaaaaa222log)3(log)2()(log) 1 (log,log,log5表示下列各式:、用例四、当堂测评:zyxzxyyzxzyx322321325 . 05 . 0776lg)3()lg()2()lg(1lg,lg,lg24log1log)3(81log8log)2(216log11)(表示下列各式:、用)(、计算:五、课堂小结本节课的主要内容是:(1)对数的运算性质以及其探究过程。(2)运算性质:若a0,且a1,M0,N0,那么 (3)应用运算性质的进行简单计算和化简。MnMNMNMNMMNanaaaaaaaloglogloglogloglogloglog六、作业布置: 习题34 A 组 5、(1)(2)(3)(4) 6、(1)(2)(3)(4)