Question

if a=9-4√5 then value of a-1/a
​

Answer 1

a=9-4√5

1/a=1/(9-4√5)

=1*(9+4√5)/(9)2-(4√5)2

=(9+4√5)/81-80

=9+4√5

a-1/a=9-4√5-(9+4√5)

=9-4√5-9-4√5

=-8√5

Answer 2

Answer:

Step-by-step explanation:

9-4root5 - 1 / 9-4root5

= 9-4root5 - 1 / 9-4root5 * 9+4root5/9+4root5

= 9-4root5 + [-9-4root5] / 9^2-[4^2*5]

= 9-4root5 + [-9-4root5]/81-80

= 9-4root5 - 9 - 4root5

= -2*4root5

=-8root5