已知log(5)35=m,用m表示log(7)1.4
问题描述:
已知log(5)35=m,用m表示log(7)1.4
答
log(5)35=m
lg35/lg5=m
(lg5+lg7)=mlg5
lg7=(m-1)lg5
log(7)1.4=lg1.4/lg7=(lg(7/5))/lg7
=(lg7-lg5)/lg7
=1-lg5/lg7
=1-1/(m-1)
=(m-2)/(m-1)