The third term of an arithmetic sequence is 7, and the 8th term is 17. Find the a1, and the common difference d?

Answer 1

a₃ = a₁ + 2d = 7

a₈ = a₁ + 7d = 17

Subtracting the equations, we get -5d = -10,

So, d = 2

a₁ = 7 - 2d = 7 - 4 = 3