Question

Find value of this,if
$x = 9 + 4 \sqrt{5}$
below is question
$x ^{4} + \frac{1}{x^{4} }$
​

Answer 1

$x ^{4} + \frac{1}{x^{4} }$

$18 + \frac{1}{9 + 4 ^{ - 4} }$

$\frac{18 \times (9 + 4^{ - 4} )}{9 + 4 ^{4} }$

=18