Question

if a=9-4 root 5 find the value of a-1/a

Answer 1

a = 9 - 4√5

1/a = (9 + 4√5)/ (81-80) = 9 + 4√5

a - 1/a = 9 - 4√5 - 9 - 4√5 = - 8√5

Answer 2

HEY USER... ✋✋

HERE IS UR ANSWER --

GIVEN,,

a = 9 - 4√5

1/a = 1/ 9 - 4√5

Now rationalize the denominator ,

= ( 1/ 9 - 4√5) * (9+4√5 / 9+4√5)

= ( 9 + 4√5) / (9)^2 - (4√5)^2

= 9 + 4√5 / 81 - 80

= 9 + 4√5 / 1

= 9 + 4√5

We know that ,,

a = 9 - 4√5

1/a = 9 + 4√5

Therefore , a - 1/a =

9 - 4√5 - (9+4√5)

= 9 - 4√5 - 9 - 4√5

= - 8√5

HOPE IT HELPS... ☺