Question

if x=9-4√5 then x2-1/x2​

Answer 1

x=9-4√5

x²-1/x²

(9-4√5)²-1/(9-4√5)²

36-72√5+80 - 1/(36-72√5+80)

216-72√5 - 1/(216-72√5)

(216-72√5)²-1)/(216-72√5)

(46656-32400√5+25920-1)/(216-72√5)

(72575-32400√5)/(216-72√5)