If (x − 1/x) = 5, Find the value of

Given, If $(x-1 / x)=5$

We know that, $(a-b)^{3}=a^{3}-b^{3}-3 a b(a-b) \ldots 1$

Substitute $(x-1 / x)=5$ in eq 1

$(x-1 / x)^{3}=x^{3}-1 / x^{3}-3\left(x^{*} 1 / x\right)(x-1 / x)$

$5^{3}=x^{3}-1 / x^{3}-3(x-1 / x)$

$125=x^{3}-1 / x^{3}-\left(3^{*} 5\right)$

$125=x^{3}-1 / x^{3}-15$

$125+15=x^{3}-1 / x^{3}$

$x^{3}-1 / x^{3}=140$

Hence, the result is $x^{3}-1 / x^{3}=140$