若log₃2=a,则log₃8-2log₃6用a表示为?1.a-2 2.5a-2.3.3a-(1+a)² 4.3a-a²-1
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![若log₃2=a,则log₃8-2log₃6用a表示为?1.a-2 2.5a-2.3.3a-(1+a)² 4.3a-a²-1](/uploads/image/z/10433222-62-2.jpg?t=%E8%8B%A5log%26%238323%3B2%3Da%2C%E5%88%99log%26%238323%3B8-2log%26%238323%3B6%E7%94%A8a%E8%A1%A8%E7%A4%BA%E4%B8%BA%3F1.a-2+2.5a-2.3.3a-%281%2Ba%29%26%23178%3B+4.3a-a%26%23178%3B-1)
若log₃2=a,则log₃8-2log₃6用a表示为?1.a-2 2.5a-2.3.3a-(1+a)² 4.3a-a²-1
若log₃2=a,则log₃8-2log₃6用a表示为?1.a-2 2.5a-2.3.3a-(1+a)² 4.3a-a²-1
若log₃2=a,则log₃8-2log₃6用a表示为?1.a-2 2.5a-2.3.3a-(1+a)² 4.3a-a²-1
log₃8-2log₃6
=log₃2³-2log₃(2×3)
=3log₃2-2(log₃2+log₃3)
=3a-2(a+1)
=3a-2a-2
=a-2
所以是1
log3(8)=3log3(2)=3a
2log3(6)log3(36)=log3(4*9)=log3(4)+log3(9)=2log3(2)+2log3(3)=2a+2
∴log3(8)-2log3(6)=3a-2a-2 =a-2
选1