Question

If a=9+4√5 ,then find the value of a- 1/a

Answer 1

a = 9 + 4√5

value of 1/a = 1/9+4√5 × 9-4√5/9-4√5

= 9-4√5 / (9)square - (4√5)square

= 9-4√5/81-80

= 9-4√5

the value of a - 1/a

= 9 + 4√5 - (9-4√5)

= 9 +4√5 -9+4√5

= 8√5

answer is 8√5

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