求函数的极限
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L =lim(x->1) [2x/(x+1) ]^[(2x)/(x-1)]
lnL
=lim(x->1) 2x.ln[2x/(x+1) ] /(x-1) (0/0 分子分母分别求导)
=lim(x->1) 2{ ln[2x/(x+1) ] + x[1/x - 1/(x+1) ] }
=lim(x->1) 2{ ln[2x/(x+1) ] + 1/(x+1) }
= 2( 0 + 1/2)
=1
=> L = e
lim(x->1) [2x/(x+1) ]^[(2x)/(x-1)] = e
lnL
=lim(x->1) 2x.ln[2x/(x+1) ] /(x-1) (0/0 分子分母分别求导)
=lim(x->1) 2{ ln[2x/(x+1) ] + x[1/x - 1/(x+1) ] }
=lim(x->1) 2{ ln[2x/(x+1) ] + 1/(x+1) }
= 2( 0 + 1/2)
=1
=> L = e
lim(x->1) [2x/(x+1) ]^[(2x)/(x-1)] = e
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