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Evaluate the following limit: limx→5[x3-125x5-3125]

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Question

Evaluate the following limit:

`lim_(x -> 5)[(x^3 - 125)/(x^5 - 3125)]`

Evaluate
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Solution

`lim_(x -> 5)[(x^3 - 125)/(x^5 - 3125)]`

= `lim_(x -> 5)(((x^3 - 5^3)/(x - 5)))/(((x^5 - 5^5)/(x - 5)))     ...[(because x -> 5"," therefore x ≠ 5","),(therefore x - 5 ≠0)]`

= `(lim_(x -> 5) (x^3 - 5^3)/(x - 5))/(lim_(x -> 5)(x^5 - 5^5)/(x - 5))`

= `(3(5)^2)/(5(5)^4)    ...[because  lim_(x -> "a") (x^"n" - "a"^"n")/(x - "a") = "n"*"a"^("n" - 1)]`

= `3/(5)^3`

= `3/125`

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Chapter 7: Limits - Exercise 7.1 [Page 139]

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