Question

obter o vigesimo termo P.A [53,50,47,...]

Answer 1

a 1 =53
a 2 = 50
r = a 2 - a 1
r = 50 - 53
r = -3
a n = a 1 + (n - 1 ).r
a 20 = 53 + (20 - 1 ). -3
a 20 = 53 + 19 . -3
a 20 = 53 +(- 57)
a 20 = 53 - 57
a 20 = -4