In an AP
Given a = 5, d = 3, a_n =50, find n and S_n.

In an AP
given a = 7, a₁₃ =35, find d and S₁₃.

In an AP
Given a₁₂ = 37, d = 3, find ‘a’ and S₁₂.

In an AP
Given d = 5, 5₉ = 75, find ‘a’ and ‘a’

70. Prove that no matter what the real numbers ‘a’ and ‘b’ are the sequence with nth term a + nb is always an A .P. what is the common difference ? What is the sum of the first 20 terms.