Question

calcule o 20 numero impar positivo (1,3,5,7)

Answer 1

a1=1
a2=3
a3=5
r=3-1=2
n=20
a20 =a1 + ( n - 1)
a20= 1 + 20 - 1) × 2
a20= 1 + 38
a20= 39