defence exam Army Havildar SAC Mock Test Series 2025 Mathematics Sequences and Series Harmonic Progressions
If a1, a2, a3, ........ are in H.P., then the expression a1a2 + a2a3 +...... + an - 1 an is equal to:
1
n(a1 - a2)
2
(n - 1)(a1 - an)
3
na1an
4
(n - 1) a1an