Question

if a=9-4root5 then find value of a-1/a

Answer 1

I hope it is helpful for you

Answer 2

a =9- [4 root 5]

1/a  = 1/[9-(4 root 5) ]        (rationalization)

1/a = 9+(4 root 5)/(81-16*5)

1/a = (9+ (4 root 5)/(81 - 80)

1/a = (9+[4 root 5])/1

1/a = 9+  4 root 5

Now,

9 - (4 root 5) - [9 + 4 root 5]

9 -( 4 root 5) - 9 - (4 root 5)

9 will cancel,

- 8 root 5



i hope this will help you



-by ABHAY