Question

Find the 10th term of the progression 1 + 3 + 5 + 7 + ...

Answer 1

This is an arithmetic progression with first term a₁ = 1 and common difference d = 2.

a_n = a₁ + (n − 1)d

a₁₀ = 1 + (10 − 1)2

a₁₀ = 1 + 9 × 2

= 1 + 18

= 19

So the 10th term is 19.