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解法一:原式=lim(x->5){[x^(1/2)+5^(1/2)]/[x^(2/3)+(5x)^(1/3)+5^(2/3)]}
(分子分母同乘[x^(1/2)+5^(1/2)]*[x^(2/3)+(5x)^(1/3)+5^(2/3)],再化简)
=[5^(1/2)+5^(1/2)]/[5^(2/3)+(5*5)^(1/3)+5^(2/3)]
=(2/3)/5^(1/6);
解法二:原式=lim(x->5){[(1/3)x^(-2/3)]/[(1/2)x^(-1/2)]}
(0/0型极限,应用罗比达法则)
=[(1/3)*5^(-2/3)]/[(1/2)*5^(-1/2)]
=(2/3)/5^(1/6)。
(分子分母同乘[x^(1/2)+5^(1/2)]*[x^(2/3)+(5x)^(1/3)+5^(2/3)],再化简)
=[5^(1/2)+5^(1/2)]/[5^(2/3)+(5*5)^(1/3)+5^(2/3)]
=(2/3)/5^(1/6);
解法二:原式=lim(x->5){[(1/3)x^(-2/3)]/[(1/2)x^(-1/2)]}
(0/0型极限,应用罗比达法则)
=[(1/3)*5^(-2/3)]/[(1/2)*5^(-1/2)]
=(2/3)/5^(1/6)。
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