对数的运算性质222333444555:(1)log4log8log32(2)log27log9log243(3)log256log16log16(4)log625log125log5计算下列各式与与与与观察上述结果,你能得到怎样的结论?问题情境log()logloglogloglogl:oglog0,1,0,0,.aaaaaanaaMNMNMMNNMnMaaMNnR对数的运其性中算质建构新知2loglog(1)log2log(0,1)?(2)log?(3)log?:aaaannaxxayxyxaaananyaya与是否是相同函数=与相同吗函数与是否辨为相同函数析建构新知例1用logax，logay，logaz表示下列各式：(1)logaxyz；(2)logax2y3z.解(1)logaxyz＝loga(xy)－logaz＝logax＋logay－logaz；(2)logax2y3z＝loga(x2y)－loga3z＝logax2＋logay－loga3z＝2logax＋12logay－13logaz.新知应用23333(23)2log521222(1)log27log9(2)2log6log4(3)log(743)71(4)loglog12log42(2)482例计算下列各式的值新知应用32.(1)xx例已知lg20.3010,lg1.080.0334,且1.08求的值精确到新知应用33224(1)lg2+lg5(2)lg2lg53lg2lg5(3)lg5lg2lg50(4)lg25lg2lg50lg2例计算新知应用22212125(1)lglg(3)1(2)lg,lg2410,lg()lg().(3),lg(lg5lg7)lglg5lg70,,.(4)2lg()lglglg2,.xxaabxxabbxxxxxxxxyxyy例解方程已知是方程的两根求已知是方程的两根求已知求新知应用
