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Rationalise the denominator of the following: 15+2 - Mathematics

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Question

Rationalise the denominator of the following:

`1/(sqrt5+sqrt2)`

Sum

Solution

The given number is `1/(sqrt5 + sqrt2)`

On rationalising the denominator,

⇒ `1/(sqrt5 + sqrt2) = 1/(sqrt5 + sqrt2) xx (sqrt5 - sqrt2)/(sqrt5 - sqrt2)`

We know that (a + b) (a - b) = a2 - b2

⇒ `1/(sqrt5 + sqrt2) = (sqrt5 - sqrt2)/((sqrt5)^2 - (sqrt2)^2)`

⇒ `1/(sqrt5 + sqrt2) = (sqrt5 - sqrt2)/(5 - 2)`

∴ `1/(sqrt5 + sqrt2) = (sqrt5 - sqrt2)/3`

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Chapter 1: Number Systems - Exercise 1.5 [Page 24]

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NCERT Mathematics [English] Class 9
Chapter 1 Number Systems
Exercise 1.5 | Q 5.3 | Page 24

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