Question

已知3

a

3

•9

a

3

=2，那么21og₉8-2log₃6用a表示是______．

Answer 1

由3

a

3

•9

a

3

=2，得3

a

3

•3

2a

3

=3a=2，
所以log₃2=a．
则21og₉8-2log₃6=log₃8-2log₃（2×3）=3log₃2-2log₃2-2=log₃2-2=a-2．
故答案为a-2．