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Question
Evaluate the following limits:
`lim_(x -> 5) (sqrt(x - 1) - 2)/(x - 5)`
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Solution
`lim_(x -> 5) (sqrt(x - 1) - 2)/(x - 5) = lim_(x -> 5) ((x - 1)^(1/2) - (4)^(1/2))/((x - 1) - 4)`
Put x – 1 = y
When x → 1
⇒ y → 5 – 1 = 4
∴ `lim_(x -> 5) (sqrt(x - 1) - 2)/(x - 5) = lim_(y -> 4) (^(1/2) - (4)^(1/2))/(y - 4)`
`lim_(x -> "a") (x^"n" - "a"^"n")/(x - "a") = "n" * "a"^("n" - 1)`
= `1/2(4)^(1/2 - 1)`
= `1/2 xx (4)^(- 1/2)`
= `1/2 xx 1/((4)^(1/2))`
= `1/2 xx 1/2`
`lim_(x -> 5) (sqrt(x - 1) - 2)/(x - 5) = 1/4`
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