lim(x-->无穷)(ln(x-1)/(x+1))/(1/x)用罗必塔法则上下求导,最后化简出lim(x-->无穷)(-2x^2)/(x^2-1)是怎么做出来的?我怎么也划不出来.

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lim(x-->无穷)(ln(x-1)/(x+1))/(1/x)用罗必塔法则上下求导,最后化简出lim(x-->无穷)(-2x^2)/(x^2-1)是怎么做出来的?我怎么也划不出来.

lim(x-->无穷)(ln(x-1)/(x+1))/(1/x)用罗必塔法则上下求导,最后化简出lim(x-->无穷)(-2x^2)/(x^2-1)是怎么做出来的?我怎么也划不出来.
lim(x-->无穷)(ln(x-1)/(x+1))/(1/x)用罗必塔法则上下求导,
最后化简出lim(x-->无穷)(-2x^2)/(x^2-1)是怎么做出来的?我怎么也划不出来.

lim(x-->无穷)(ln(x-1)/(x+1))/(1/x)用罗必塔法则上下求导,最后化简出lim(x-->无穷)(-2x^2)/(x^2-1)是怎么做出来的?我怎么也划不出来.
分子求导=(x+1)/(x-1)*[(x-1)/(x+1)]'
=(x+1)/(x-1)*(x+1-x+1)/(x+1)²
=2/(x+1)(x-1)
=2/(x²-1)
分母求导=-1/x²
所以得到-2x²/(x²-1)