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Evaluate the following limits: limx→0[1+x3-1+xx] - Mathematics and Statistics

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Question

Evaluate the following limits: `lim_(x -> 0)[(root(3)(1 + x) - sqrt(1 + x))/x]`

Sum

Solution

`lim_(x -> 0)(root(3)(1 + x) - sqrt(1 + x))/x`

= `lim_(x -> 0)((1 + x)^(1/3) - (1 + x)^(1/2))/x`

Put 1 + x = y
As x → 0, y → 1

∴ `lim_(x -> 0)((1 + x)^(1/3) - (1 + x)^(1/2))/x`

= `lim_(y -> 1)(y^(1/3) - y^(1/2))/(y - 1)`

= `lim_(y -> 1)((y^(1/3) - 1) - (y^(1/2) - 1))/(y - 1)`

= `lim_(y -> 1)((y^(1/3) - 1)/(y - 1) - (y^(1/2) - 1)/(y - 1))`

= `lim_(y -> 1) (y^(1/3) - 1^(1/3))/(y - 1) - lim_(y -> 1)(y^(1/2) - 1^(1/2))/(y - 1)`

= `1/3(1)^((-2)/3) - 1/2(1)^((-1)/2)    ...[because lim_(x -> "a") (x^"n" - "a"^"n")/(x - "a") = "na"^("n" - 1)]`

= `1/3 - 1/2`

= `(2 - 3)/6`

= `-1/6`

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Chapter 7: Limits - EXERCISE 7.1 [Page 100]
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