2ãB
y=âxln(1-x)
x>=0
1-x>0
x<1
å®ä¹åï¼[0,1)
3ãC
âµ0<a<1
â´f(x)=loga xå¨å®ä¹åå
æ¯åå½æ°
f(x)max=3f(x)min
loga a=3loga 2a
loga a=loga (2a)^3
a=8a^3
8a^3-a=0
a(8a^2-1)=0
âµ0<a<1
â´8a^2-1=0
a^2=1/8
a=â2/4
6ãD
设g(x)=log1/2 x
åf(x)=|log1/2 x|=|g(x)|
âµg(x)æ¯åå½æ°ï¼ä¸å¨x>=1æ¶ï¼g(x)<=0
â´å¨x>=1æ¶ï¼|g(x)|>0ï¼å¹¶ä¸æ¯å¢å½æ°ã
å³ï¼f(x)=|g(x)|å¨[1,+â)ä¸æ¯å¢å½æ°ã
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