Question

ifa=9-4 √ 5,find the value of a-1/a

Answer 1

a= 9-4√5
1/a= 1/ (9-4√5)
rationalizing above
1/a= 9+4√5/ (9+4√5)(9-4√5)
1/a= 9+4√5/ 81-80
1/a= 9+4√5
a-1/a = (9-4√5) - (9+4√5)
= 8√5
hope it helps
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