Question

if a=6-5root , then find A square +1/A square?

Answer 1

${a}^{2} = {(6 - \sqrt{5}) }^{2}$
$= {6}^{2} + { \sqrt{5} }^{2} - 12 \sqrt{5} \\ = 36 + 5 - 12 \sqrt{5} \\ = 39 - 12 \sqrt{5}$
$\frac{1}{a} = \frac{1}{6 - \sqrt{5} } \\ = \frac{1(6 - \sqrt{5)} }{(6 - \sqrt{5} (6 + \sqrt{5}) } \\ = \frac{6 + \sqrt{5} }{ {(6)}^{2} - {( \sqrt{5} )}^{2} } \\ = \frac{6 + \sqrt{5} }{36 - 5} \\ = \frac{6 + \sqrt{5} }{31}$

Answer 2

........... hope u understand it