已知函数f(x)=log3(x/27)*log3(ax).(1/27扫码下载作业帮搜索答疑一搜即得
问题描述：
已知函数f(x)=log3(x/27)*log3(ax).(1/27
扫码下载作业帮
搜索答疑一搜即得
答
f(x)=(log3x-3)log3x
log3x单调函数故只需要代入边界值
f(1/27)=18
f(9)=-2
答
f(x)=(log3x-log327)(log3a+log3x)
f(x)=(log3x-3)(log3a+log3x)
t=log3x
f(t)=(t-3)(log3a+t)
f(t)=log3at+t^2-3log3a-3t
f(t)=t^2+(log3a-3)t-3log3a
f(t)=(t-(log3a-3)/2)^2-(log3a-3)^2/4-3log3a
1/27