Question

if x=9+4root5 find value of x2+1/x2

Answer 1

x = 9+4√5
x² = (9+4√5)² = (81+80+72√5) = 161+72√5
x²+1/x² = 161+72√5 + 1/(161+72√5) = (25921+25920+23184√5+1)/(161+72√5) = (51482+23184√5)/(161+72√5) = 322