Question

determine o numero de termos das progressoes aritmeticas:
(3,11,19,...75)

Answer 1

PA

a1 = 3
an = 75
r = 11 - 3 = 8 
n = ?

an = a1 + ( n - 1 ) . r
75 = 3 + ( n - 1 ) . 8
75 = 3 + ( 8n  - 8 )
75 = 3 + 8n - 8 
75 - 3 + 8 = 8n
80 = 8n
8n = 80
n = 80/8
n = 10

A PA tem 10 termos.

PA = ( 3 , 11, 19, 27, 35, 43, 51, 59, 67, 75)