高中数学,怎么做呢?
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解:
(1)由题知,满足对数真数大于零 (x+1)埋毕/(x-1)>0
即(弯郑芹丛唤x+1)·(x-1)>0 解得 x∈(-∞,-1)U(1,+∞)
(2)方法:对f(x)求导,并讨论f `(x)在(1,+∞)大或小于零,进而可知原函数增减
f `(x)=[log(1/2)(X+1)/(X-1)] `= 【1/[(x+1)/(x-1)]ln(1/2)】·[-2/(X-1)^2]
当X∈(1,+∞)时,[1/[(x+1)/(x-1)]ln(1/2)]< 0; [-2/(X-1)^2]< 0
则f `(x)=[1/Xln(1/2)]·[-2/(X-1)^2]> 0
f(X)在(1,+∞)上单调递增
(1)由题知,满足对数真数大于零 (x+1)埋毕/(x-1)>0
即(弯郑芹丛唤x+1)·(x-1)>0 解得 x∈(-∞,-1)U(1,+∞)
(2)方法:对f(x)求导,并讨论f `(x)在(1,+∞)大或小于零,进而可知原函数增减
f `(x)=[log(1/2)(X+1)/(X-1)] `= 【1/[(x+1)/(x-1)]ln(1/2)】·[-2/(X-1)^2]
当X∈(1,+∞)时,[1/[(x+1)/(x-1)]ln(1/2)]< 0; [-2/(X-1)^2]< 0
则f `(x)=[1/Xln(1/2)]·[-2/(X-1)^2]> 0
f(X)在(1,+∞)上单调递增
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