Question

If a_n denotes the nth term of the AP 2, 7, 12, 17, ..., find the value of (a₃₀ - a₂₀).

Answer 1

The given AP is 2, 7, 12, 17,………
Here, a = 2 and d = 7 - 2 = 5

∴ a₃₀ - a₂₀

=[ 2 +(30-1) × 5]-[2+(20-1) ×5]                    [a_n = a+ (n-1) d]

= 147-97

=50

Hence, the required value is 50.