已知lg2=a,lg3=b,求log12 5

已知lg2=a,lg3=b,求log12 5

log(a)N=log(m)N/log(m)a
log(12)5
=lg5 / lg12
=lg(10/2)/ lg(3x4)
=(1-lg2)/(lg3+lg4)
=(1-lg2)/(lg3+2lg2)
=(1-a)/(b+2a)