If x + 1/x = 2K, then what is the value of x^4 +1/(x^4) ?

If $x + \frac{1}{x} = 2K$

then what is the value of $x^4 +\frac{1}{x^4}$ = ?

$(x + \frac{1}{x}) = x$

(x² + x^-2) = (x)² - 2 = b

= (x⁴ + x^-4) = b² - 2

If $x + \frac{1}{x} = 2K$

(x² + x^-2) = (2k)² - 2 = 4k² - 2

$x^4 +\frac{1}{x^4}$ = (4k² - 2)² - 2

$x^4 +\frac{1}{x^4}$ = 16k⁴ + 4 - 16k - 2

$x^4 +\frac{1}{x^4}$ = $16K^4 - 16K^2 +2$