高中数学 221对数与对数运算(二)课件 新人教A版必修1 课件VIP免费

2.2.1对数与对数运算复习引入一般地，如果(a＞0,a≠1)的b次幂等于N，就是ab＝N，那么数b叫做以a为底N的对数，记作：logaN＝b.其中a(0,1)(1,∈∪＋∞)；N(0,∈＋∞).b(-∞,∈＋∞).2．指数式与对数式的互化.logNaNabNNaablog3．要点回顾(1)负数与零没有对数；(2)loga1＝0，logaa＝1；(3)对数恒等式练习：求下列各式中的x0)(loglog)1(52x1)(lglog)2(3x1log:5x解5x3lg:x解310x1000x4．指数运算法则),,(Rnmaaanmnm),,()(Rnmaamnnm).()(Rnbaabnnn游戏一maM设naNnmaNM则mMalognNalognmNMa)(logNMNMaaaloglog)(log你能类似地玩出下列公式吗？NMNMaaalogloglog游戏二MaMalognnMaMa)(lognManMalogMnManaloglog)(Rn1．积、商、幂的对数运算法则：如果a＞0，且a≠1，M＞0，N＞0有：)3(loglog)2(logloglog)1(loglog)(logR)(nMnMNMNMNMMNanaaaaaaa“积的对数＝对数的和”……①有时逆向运用公式：②真数的取值范围必须是(0,＋∞).③对公式容易错误记忆，要特别注意：.loglog)(logNMNMaaa.110log2log5log101010如：NMMNaaaloglog)(log)3(loglog)2(logloglog)1(loglog)(logR)(nMnMNMNMNMMNanaaaaaaa32log)2(;(1)logzyxzxyaa例1用logax，logay，logaz表示下列各式：例题与练习练习课本P68练习1)3(loglog)2(logloglog)1(loglog)(logR)(nMnMNMNMNMMNanaaaaaaa例2计算例题与练习25log)1(51log)2(4.0)24(log(3)5725100lg)4(练习课本P68练习2、3)3(loglog)2(logloglog)1(loglog)(logR)(nMnMNMNMNMMNanaaaaaaa例3计算例题与练习50lg2lg)5(lg)2(25lg20lg)1(18lg7lg37lg214lg)3()3(loglog)2(logloglog)1(loglog)(logR)(nMnMNMNMNMMNanaaaaaaa课堂小结1.对数的运算法则；2.公式的逆向使用.例4例题与练习.45lg求，已知3010.02lg，4771.03lg)3(loglog)2(logloglog)1(loglog)(logR)(nMnMNMNMNMMNanaaaaaaa1．课本P74A组3、4、5；2．阅读思考《导学》P39~40；3.记得预习。课后作业