Using the identity,
(a+b)2=a2+2ab+b2,
a2+b2=(a+b)2−2ab.
So, a2+1a2=(a+1a)2−2
(i) Given that a+1a=4
⟹a2+1a2=(a+1a)2−2=42−2
a2+1a2=16−2=14
(ii) Given that a+1a=6
⟹a2+1a2=(a+1a)2−2=62−2
a2+1a2=36−2=34
Using identity,
(a−b)2=a2−2ab+b2,
a2+b2=(a−b)2+2ab.
So, a2+1a2=(a−1a)2+2
(iii) Given that a−1a=5
⟹a2+1a2=(a−1a)2+2=52+2=27
(iv) Given that a−1a=3
⟹a2+1a2=(a−1a)2+2=32+2=11