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What is the value of : [(x - 64)^(1/3) - 4]/x for x tending to 0?

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carolinesmiths | Student, Kindergarten | (Level 1) Salutatorian

Posted June 18, 2011 at 3:35 PM via web

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What is the value of : [(x - 64)^(1/3) - 4]/x for x tending to 0?

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giorgiana1976 | College Teacher | (Level 3) Valedictorian

Posted June 18, 2011 at 3:40 PM (Answer #1)

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In other words, we'll have to evaluate the limit of the fraction, if x approaches to 0:

We'll replace x by 0, we'll get:

lim [(x - 64)^(1/3) - 4]/x = [(0 - 64)^(1/3) - 4]/0

lim [(x - 64)^(1/3) - 4]/x = [(-64)^(1/3) - 4]/0

But (-64)^(1/3) = -4

lim [(x - 64)^(1/3) - 4]/x = (-4 - 4)/0

lim [(x - 64)^(1/3) - 4]/x = -8/0

lim [(x - 64)^(1/3) - 4]/x = - infinite

When x approches to 0, the value of the fraction [(x - 64)^(1/3) - 4]/x tends to - infinite.

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted June 18, 2011 at 3:44 PM (Answer #2)

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We have to find the value of lim x-->0 [(x - 64)^(1/3) - 4]/x

lim x-->0 [(x - 64)^(1/3) - 4]/x

If we substitute x = 0 in the denominator we get 0 and substituting x in the numerator gives -4 - 4 = -8.

As x tends to 0 the given expression tends to an exceedingly large negative value or to -infinity.

The required value of lim x-->0 [(x - 64)^(1/3) - 4]/x = -inf.

 

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