Question

determine o vigesimo termo da p.a. (2,5,8,...)

Answer 1

razão = 5-8=3
n=20
a1= 2

an=a1+ (n-1)x r
a20 = 2 + (20 - 1) x 3
a20 = 2 + 19 x 3
a20 = 2 +57
a20 = 59