1题 (lg根号2+lg3-lg根号10)/lg1.8
1个回答

(lg根号2+lg3-lg根号10)/lg1.8

=lg(√2*√9/√10)/lg1.8

=lg√1.8/lg1.8

=(1/2)*lg1.8/lg1.8

=1/2

log6(7)=a

lg7/(lg2+lg3)=a

lg7=alg2+alg3

log3(4)=b

2lg2/lg3=b

lg2=(b/2)lg3

所以lg7=a(b/2)lg3+alg3=(a+ab/2)lg3

log12(7)

=lg7/(2lg2+lg3)

=(a+ab/2)lg3/[2*(b/2)lg3+lg3]

=(a+ab/2)/[2*(b/2)+1]

=(2a+ab)/(2b+2)