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Rationalise the denominator of the following: 35+35-3 - Mathematics

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Question

Rationalise the denominator of the following:

`(3sqrt(5) + sqrt(3))/(sqrt(5) - sqrt(3))`

Sum

Solution

Let `E = (3sqrt(5) + sqrt(3))/(sqrt(5) - sqrt(3))`

For rationalising the denominator, multiplying numerator and denominator by `sqrt(5) + sqrt(3)`,

`E = (3sqrt(5) + sqrt(3))/(sqrt(5) - sqrt(3)) xx (sqrt(5) + sqrt(3))/(sqrt(5) + sqrt(3))`

= `(3sqrt(5)(sqrt(5) + sqrt(3)) + sqrt(3)(sqrt(5) + sqrt(3)))/((sqrt(5))^2 - (sqrt(3))^2`  ...[Using identity, (a + b)(a – b) = a2 – b2]

= `(15 + 3sqrt(15) + sqrt(15) + 3)/(5 - 3)`

= `(18 + 4sqrt(15))/2`

= `9 + 2sqrt(15)`

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Chapter 1: Number Systems - Exercise 1.3 [Page 10]

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NCERT Exemplar Mathematics [English] Class 9
Chapter 1 Number Systems
Exercise 1.3 | Q 10. (viii) | Page 10

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