Respuesta :

reinhard10158

Step-by-step explanation:

arithmetic sequence means that every new term is created by adding a certain constant (here 2) to the previous term.

a27 = -1/2 = a1 + (n-1)×2 = a1 + 26×2 = a1 + 52

a1 = -52 1/2 = -105/2

an = -105/2 + (n-1)×2