Question

if a=9-4√5find the value of a^2+1/a^2​

Answer 1

Answer:

A = 9-4√5

1/a=1/(9-4√5)

=9+4√5/(9)^2-(4√5)^2

=9+4√5/(81-80)

=9+4√5

a^2-(1/a)^2=[9-4√5]-[9+4√5]^2]

=81+80-72√5-(81+80+72√5)

81+80-72√5-81-80-72√5

80 and 81 gets cancelled

(-72-72)√5

= -144√5