Question

encontre os numeros de termos da p.a (-20,-16,-12....12)

Answer 1

an = a1 + ( n - 1 ) . r
12 = -20 + ( n - 1 ) . 4
-20 + 4n - 4 = 12
4n = 12 + 24
4n = 36
n = 36 / 4
n = 9