If x4 + 1/(x^4) = 27887, the positive value of (x + 1/x - 13 ) is:

If x⁴ + \(\frac{1}{x^4}\) = a

then x² + \(\frac{1}{x^2}\) = \(\sqrt {a + 2}\) = b

and x + \(\frac{1}{x}\) = \(\sqrt {b + 2}\)

ATQ,

x⁴ + \(\frac{1}{x^4}\) = 27887

x² + \(\frac{1}{x^2}\) = \(\sqrt {27887 + 2}\) = 167

So, ( x + \(\frac{1}{x}\) - 13 ) = ( \(\sqrt {167 + 2}\) - 13 ) = 0