Find the rationalising factor of $4-\sqrt{5}$.

To do: To find the rationalising factor of $4-\sqrt{5}$.

Solution:

Given $4-\sqrt{5}$

On multiplying the given number by $4+\sqrt{5}$.

$( 4-\sqrt{5})( 4+\sqrt{5})$

$=4^2-( \sqrt{5})^2$

$=16-5$

$=11$, a rational number.

Thus, $4+\sqrt{5}$ is a rationalising factor of  $4-\sqrt{5}$.

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Updated on: 10-Oct-2022

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