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Evaluate: limx→2x4-4x2+32x-8

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Question

Evaluate: `lim_(x -> sqrt(2)) (x^4 - 4)/(x^2 + 3sqrt(2x) - 8)`

Sum
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Solution

Given that `lim_(x -> sqrt(2)) (x^4 - 4)/(x^2 + 3sqrt(2x) - 8)`

= `lim_(x -> sqrt(2)) ((x^2 - 2)(x^2 + 2))/(x^2 + 4sqrt(2x) - sqrt(2x) - 8)`

= `lim_(x -> sqrt(2)) ((x + sqrt(2))(x - sqrt(2))(x^2 + 2))/(x(x + 4sqrt(2)) - sqrt(2)(x + 4sqrt(2))`

= `lim_(x -> sqrt(2)) ((x + sqrt(2))(x - sqrt(2))(x^2 + 2))/((x + 4sqrt(2))(x - sqrt(2))`

= `lim_(x -> sqrt(2)) ((x + sqrt(2))(x^2 + 2))/(x + 4sqrt(2))`

Taking limits we have

= `((sqrt(2) + sqrt(2))(2 + 2))/(sqrt(2) + 4sqrt(2))`

= `(2sqrt(2) xx 4)/(5sqrt(2))`

= `8/5`.

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Chapter 13: Limits and Derivatives - Exercise [Page 240]

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NCERT Exemplar Mathematics Exemplar [English] Class 11
Chapter 13 Limits and Derivatives
Exercise | Q 9 | Page 240

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