Question

Given a = 6 + √3
⇒ (1/a) = 1 / (6 + √3)
Multiply and divide by (6 − √3)
⇒ (1/a) = (6− √3) / [(6 + √3)(6 − √3)]
⇒ (1/a) = (6 − √3) / [36 − 3]
⇒ (1/a) = (6− √3)/33
∴ a - (1/a) = (6 + √3) -(6 − √3)/33
= [33(6 + √3) - (6 - √3)]/33
= [32*6 + 34*√3]/33
= [192 + 34√3]/33

Answer : [192 + 34√3]/33

Why does 1/a come above

Answer 1

Don't worry. It is a kind of method used to solve these kinds of questions.
If we find 1/a, then we can easily solve the problem.

So please follow the steps in the answer.
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practise more problems of these kinds and later you can do t by yourself