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Match the LIST-I with LIST-II If a = (√5 − 2)/(√5 + 2), then match the following: LIST-I ​LIST-II​ A. a + 1/a I. 8√5 B. 1/a − a II.
Question

Match the LIST-I with LIST-II
If a = (√5 − 2)/(√5 + 2), then match the following:

LIST-I
LIST-II
A. a + 1/a
I. 8√5
B. 1/a − a
II. 161
C. 1/2(a² + 1/a²)
III. 18
D. 1/a² − a²
IV. 144√5

Choose the correct answer from the options given below:

A.

A-IV, B-I, C-III, D-II

B.

A-III, B-I, C-II, D-IV

C.

A-I, B-II, C-III, D-IV

D.

A-I, B-III, C-II, D-IV

Correct option is B

Given:
a = (√5 − 2)/(√5 + 2)
Formula:
(a + 1/a)² = a² + 1/a² + 2
Solution:
a = (√5 − 2)/(√5 + 2)
Rationalising,
a = (√5 − 2)²/(5 − 4)
= 9 − 4√5
Therefore,
1/a = 9 + 4√5
Now,
A.
a + 1/a
= 9 − 4√5 + 9 + 4√5
= 18
Therefore, A → III.
B.
1/a − a
= 9 + 4√5 − 9 + 4√5
= 8√5
Therefore, B → I.
Also,
C.
a² + 1/a²
= (a + 1/a)² − 2
= 18² − 2
= 324 − 2
= 322
Therefore,
1/2(a² + 1/a²)
= 322/2
= 161
Therefore, C → II.
Now, D.
1/a² − a²
= (1/a − a)(1/a + a)
= 8√5 × 18
= 144√5
Therefore, D → IV.
Hence, the correct matching is:
A-III, B-I, C-II, D-IV
Hence, the correct answer is Option (b).

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