Question

x-1/x=3 then find (x^3-1/x^3) URGENT PLZ

Answer 1

Given Equation is x - 1/x = 3

On cubing both sides, we get

= > (x - 1/x)^3 = (3)^3

= > x^3 - 1/x^3 - 3 * x * 1/x(x - 1/x) = 27

= > x^3 - 1/x^3 - 3(3) = 27

= > x^3 - 1/x^3 - 9 = 27

= > x^3 - 1/x^3 = 27 + 9

= > x^3 - 1/x^3 = 36.



Hope this helps!

Answer 2

Hello friends!!

Here is your answer :

Given,

$x - \frac{1}{x} = 3$


To find

${x}^{3} - \frac{1}{ {x}^{3} }$

Solution


$x - \frac{1}{x} = 3$

Cube both sides,


${(x - \frac{1}{x} )}^{3} = {(3)}^{3}$



Using identity :

( a - b ) = a³ - b³ - 3ab ( a - b )


${(x)}^{3} - {( \frac{1}{x}) }^{3} - 3(x)( \frac{1}{x} )(x - \frac{1}{x} ) = 3 \times 3 \times 3$


${x}^{3} - \frac{1}{ {x}^{3} } - 3(3) = 27$


${x}^{3} - \frac{1}{ {x}^{3} } - 9 = 27$


${x}^{3} - \frac{1}{ {x}^{3} } = 27 + 9$



${x}^{3} - \frac{1}{ {x}^{3} } = 36$


Hope it helps you...

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