Question

if x=2+√5 then find the value of x^2-4x-1

Answer 1

Hey mate!


Here is yr answer
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Given,

x = 2 + √5


=> x² - 4x - 1

=> ( 2+√5 )² - 4( 2+√5 ) -1

=> ( 4 + 5 ) - 8 + 4√5 -1

=> 9 - 8 + 4√5 -1

=> 4√5


Therefore, value of x² - 4x -1 is 4√5


Hope it hlpzz....

Answer 2

Hey mate!

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Given :

$\mathsf{x = 2 + \sqrt{5}}$

To find :

$\mathsf{x {}^{2} - 4x - 1}$

Solution :

$\mathsf{(2 + \sqrt{5}) {}^{2} - 4(2 + \sqrt{5}) - 1 } \\ \\ \mathsf{2 {}^{2} + \sqrt{5} {}^{2} + 2 \: . \: 2 \: . \: \sqrt{5} - 8 - 4 \sqrt{5} - 1 } \\ \\ \mathsf{ 4 + 5 + 4 \sqrt{5} - 8 - 4 \sqrt{5} - 1} \\ \\ \mathsf{ \cancel{ \: 9 } + \cancel{ 4 \sqrt{5}} - \cancel { \: 9} - \cancel{4 \sqrt{5} }} \\ \\ \mathsf{ = 0}$

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Thanks for the question !

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