当log1/2(3x-2)<=log2(x)时,则f(x)=log1/2(3x-2)
此时,3x-2>0,且x>0,且1/(3x-2)<=x
解得x>=1
则3x-2>=1
log1/2(3x-2)<=0
即f(x)<=0
当log1/2(3x-2)>log2(x)时,则f(x)=log2(x)
此时,3x-2>0,且x>0,且1/(3x-2)>x
解得2/3
1. log(1/2) (3x-2)=log2 1/(3x-2)≤log2 x时
f(x)=log1/2 (3x-2)
根据对数性质3x-2>0 x>2/3
且1/(3x-2)≤x
即3x²-2x-1≥0
(3x+1)(x-1)≥0
解得x≤-1/3或x≥1
所以x≥1
2. log(1/2) (3x-2)=log2 1/(3x-2)>log2时
f(x)=log2 x
根据对数性质 x>0 且仍然要x>2/3
且1/(3x-2)>x
即3x²-2x-1<0
(3x+1)(x-1)<0
解得-1/3
f(x)=log1/2(3x-2)*log2(x)=-log2(3x-2)*log2(x) ——换底公式
因为底数为2,大于1,所以:
当log2(3x-2)<=log2(x)时,即当3x-2<=x时,亦即当x<=1时,f(x)=-log2(3x-2)
而3x-2>0这是满足定义域的要求,所以此时2/3
当log2(3x-2)>log2(x)时,即当3x-2>x时,亦即当x>1时,f(x)=-log2(x),又f(x)底数大于1,
所以log2(x)>0,即f(x)<0
综上可知,f(x)的值域为一切实数,定义域为x>2/3.
log1/2(3x-2)<=log2(x)时,-log2(3x-2)<=log2(x),移项,得到Log2(3x^2-2x)>=0即3x^2-2x>=1
解得x>=1或x<=-1/3,又3x-2>0,得到x>2/3,所以x>=1
所以当x>=1时,f(x)=log1/2(3x-2)<=f(1)=0
log1/2(3x-2)>log2(x)时,得到0<3x^2-2x<1,解得-1/3
定义域:x>=2/3,f(x)可以转化成f(x)=log2[1/(3x-2)]*log 2(x),当1/(3x -2)<=x时,f(x)=log1/2(3x -2),解得x>=1 ,f(x)<=0,同理,当1/(3x-2)>x 时,f(x)=log2x,解得2/3<=x<1,log2(2/3)<=f(x)<0
两点四十一