Question

The 20th term of an arithmetic progression 1,5,9,13......​

Answer 1

a₂₀ = 77

Explanation:

There is a common difference between consecutive terms , that is

5 - 1 = 9 - 5 = 13 - 9 = 4

This indicates the sequence is arithmetic with nth term

`a_(n)` = a₁ + (n - 1)d

where a₁ is the first term and d the common difference

Here a₁ = 1 and d = 4 , then

a₂₀ = 1 + (19 × 4) = 1 + 76 = 77