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Rationalise the denominator of the following: 43+5248+18 - Mathematics

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Question

Rationalise the denominator of the following:

`(4sqrt(3) + 5sqrt(2))/(sqrt(48) + sqrt(18))`

Sum

Solution

Let `E = (4sqrt(3) + 5sqrt(2))/(sqrt(48) + sqrt(18))`

= `(4sqrt(3) + 5sqrt(2))/(sqrt(16 xx 3) + sqrt(9 xx 2))`

= `(4sqrt(3) + 5sqrt(2))/(4sqrt(3) + 3sqrt(2))`

For rationalising the denominator, multiplying numerator and denominator by `4sqrt(3) - 3sqrt(2)`,

 = `(4sqrt(3) + 5sqrt(2))/(4sqrt(3) + 3sqrt(2)) xx ((4sqrt(3) - 3sqrt(2)))/((4sqrt(3) - 3sqrt(2))`

= `(4sqrt(3)(4sqrt(3) - 3sqrt(2)) + 5sqrt(2) (4sqrt(3) - 3sqrt(2)))/((4sqrt(3))^2 - (3sqrt(2))^2`    ...[Using identity, (a + b)(a – b) = a2 – b2]

= `(48 - 12sqrt(6) + 20sqrt(6) - 30)/30`  

= `(18 + 8sqrt(6))/30`

= `(9 + 4sqrt(6))/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. (ix) | Page 10

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