(2/3)^x=1/20 lg2=0.3010 lg3=0.4771求x

问题描述:

(2/3)^x=1/20 lg2=0.3010 lg3=0.4771
求x

x*lg(2/3)=lg(1/20)=-lg20
lg(2/3)=lg2-lg3
lg20=lg2*10=lg2+lg10=lg2+1
所以x=-(lg2+1)/(lg2-lg3)=-5.8546