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Evaluate the following limits: limy→0[1-y2-1+y2y2] - Mathematics and Statistics

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Question

Evaluate the following limits: `lim_(y -> 0) [(sqrt(1 - y^2) - sqrt(1 + y^2))/y^2]`

Sum

Solution

`lim_(y -> 0) [(sqrt(1 - y^2) - sqrt(1 + y^2))/y^2]`

= `lim_(y -> 0) [(sqrt(1 - y^2) - sqrt(1 + y^2))/y^2 xx (sqrt(1 - y^2) + sqrt(1 + y^2))/(sqrt(1 - y^2) + sqrt(1 + y^2))]`

= `lim_(y -> 0) ((1 - y^2) - (1 + y^2))/((sqrt(1 - y^2) + sqrt(1 + y^2))`

= `lim_(y -> 0) (1 - y^2 - 1 - y^2)/(y^2(sqrt(1 - y^2) + sqrt(1 + y^2))`

= `lim_(y -> 0) (-2y^2)/(y^2(sqrt(1 - y^2) + sqrt(1 + y^2))`

= `lim_(y -> 0) (-2)/(sqrt(1 - y^2) + sqrt(1 + y^2))                  ...[(because y -> 0","  therefore y ≠ 0","),(therefore y^2 ≠ 0)]`

= `(-2)/(sqrt(1 - 0^2) + sqrt(1 + 0^2)`

= `(-2)/(1 + 1)`

= `(-2)/2`

= –1

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Rationalization Method
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Chapter 7: Limits - EXERCISE 7.3 [Page 103]
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