lim|x趋向于0+ ln(1+2x^2)/x^2 = 2,

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lim|x趋向于0+ ln(1+2x^2)/x^2 = 2,
lim|x趋向于0+ ln(1+2x^2)/x^2 = 2,

lim|x趋向于0+ ln(1+2x^2)/x^2 = 2,
解法一:原式=lim(x->0)[(4x/(1+2x²))/(2x)] (0/0型极限,应用罗比达法则)
=lim(x->0)[2/(1+2x²)]
=2/(1+0)
=2;
解法二:原式=lim(x->0){ln[(1+2x²)^(x²)]}
=ln{lim(x->0)[(1+2x²)^(x²)]}
=ln{lim(x->0)[(1+2x²)^(1/(2x²))]²}
=ln{lim(x->0)[(1+2x²)^(1/(2x²))]}²
=ln(e²) (应用重要极限lim(z->0)[(1+z)^(1/z)]=e)
=2lne
=2.

这是等价无穷小代换
x→0,lnx~x,ln(1+2x^2)~2x^2
代入即可

原式=lim ln((1+2x^2)^(1/x^2))
令u=2x^2 当x趋于0+时,u趋于0+
所以原式=lim(u趋于0+) ln((1+u)^(1/u))^2=ln e^2=2