高一数学 指数函数 求解

如题所述

第1个回答  2013-08-06
1------ alg3=m, blg4=m,1/a+1/b=(lg3+lg4)/lgm=2;lg3+lg4=2lgm=lgm^2=lg12
m=√12;
2--- xlg3=ylg4=zlg6= t
xlg3 = 2y lg2 = zlg2 + zlg3
1/x=lg3/t
1/y=2lg2/t; 1/(2y)=lg2/t;
1/z=(lg2+lg3)/t
1/z-1/x= lg2/t = 1/(2y)
3--
log(a为底)18=m= 2log(a为底)3+log(a为底)2
log(a为底)24=n= log(a为底)3+3log(a为底)2
4m-3n=[log(a为底)3-log(a为底)2] * 5

log(a为底)1.5=log(a为底)3-log(a为底)2=(4m-3n)/5
4--
log(2为底)3 =a
log(3为底)7 =b
lg3/lg2=a,lg2=lg3/a
lg7/lg3=b,lg7=blg3
log(42为底)56=lg56/lg42=(lg7 + 3lg2)/(lg2+lg3+lg7) =(3/a+b)/(1/a+1+b)
5---
原式=(lgb/lga)(lgc/lgb)(lga/lgc) = 1
6--- 原式=(lg1/25)/(lg2)(lg1/8)/(lg3)(lg1/9)/(lg5)
=-2(lg5/lg2)*(-3)(lg2/lg3)*(-2)(lg3/lg5)=-12
第2个回答  2013-08-06

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第3个回答  2013-08-06
(1)2根号3
(2)
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