由换底公式log6(7)=ln7/ln6=a,ln2+ln3=ln7/alog3(4)=2ln2/ln3=b,ln2=bln3/2所以(b/2+1)ln3=ln7/a,ln3=ln7/(a*(b/2+1))log12(7)=ln7/ln12=ln7/(ln3+2ln2)=ln7/(ln3+bln3)=ln7/ln3*1/(b+1)=a*(b/2+1)/(b+1)=a(b+2)/(2b...