求这个函数的极限
3个回答
展开全部
x^(1/3) -1
=[x^(1/6) -1 ].[x^(1/6) +1 ]
x^(1/2) -1
= [x^(1/6) ]^3 -1
= (x^(1/6) -1) .[x^(1/3)+ x^(1/6) +1]
/
lim(x->1) [x^(1/3) -1]/[x^(1/2) -1]
=lim(x->1) [x^(1/6) -1 ].[x^(1/6) +1 ]/{ (x^(1/6) -1) .[x^(1/3)- x^(1/6) +1]}
=lim(x->1) [x^(1/6) +1 ]/[x^(1/3)+ x^(1/6) +1]
=(1+1)/(1+1+1)
=2/3
=[x^(1/6) -1 ].[x^(1/6) +1 ]
x^(1/2) -1
= [x^(1/6) ]^3 -1
= (x^(1/6) -1) .[x^(1/3)+ x^(1/6) +1]
/
lim(x->1) [x^(1/3) -1]/[x^(1/2) -1]
=lim(x->1) [x^(1/6) -1 ].[x^(1/6) +1 ]/{ (x^(1/6) -1) .[x^(1/3)- x^(1/6) +1]}
=lim(x->1) [x^(1/6) +1 ]/[x^(1/3)+ x^(1/6) +1]
=(1+1)/(1+1+1)
=2/3
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展开全部
利用分母立方差公式
a³-b³=(a-b)(a²+ab+b²)
极限=1/(a²+ab+b²)
=1/(1+1+1)
=1/3
a³-b³=(a-b)(a²+ab+b²)
极限=1/(a²+ab+b²)
=1/(1+1+1)
=1/3
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