例1:若60a=3,60b=5.求121−a−b2(1−b)的值.

问题描述:

例1:若60a=3,60b=5.求12

1−a−b
2(1−b)
的值.

∵60a=3,60b=5
∴a=log603,b=log605,
1-b=1-log605=log6012,
1-a-b=1-log603-log605=log604,

1−a−b
1−b
=
log604
log6012
=log124,
12
1−a−b
2(1−b)
12
1
2
log124
=12log122=2.