Question

Determine o 15° termo geral de cada P.A
A) (2,7, ...)
B) (-1, 5, ....)

Answer 1

A) P.A.(2,7,...)
r = a 2 - a 1
r = 7 - 2
r = 5
a 15 = a 1 + (n - 1 ).r
a 15 = 2 + (15 - 1 ) . 5
a 15 = 2 + 14 . 5
a 15 = 2 + 70
a 15 = 72

B) P.A.(-1,5,...)
r = a 2 - a 1
r = 5 - ( - 1)
r = 5 + 1
r = 6
a 15 = a 1 + (n - 1 ). r
a 15 = -1 + (15 - 1 ) . 6
a 15 = -1 + 14 . 6
a 15 = - 1 + 84
a 15 = 83