Question

na PA (7 , 4 , 1 , .. ) obtenha

Answer 1

PA( 7,4,1.....)
TERMO GERAL- An=a1+(n-1)r
An=7+(n-1).-3
An=7-3n+3
An= 10-3n

a13=10-3.13
a13= 10-39
a13= -29      verff.(7,4,1,-2,-5,-8,-11,-14,-17,-20,-23,-26,-29)

Answer 2

Resolvendo :
a) Termos gersl da P.A
a1 =7
a2=4
r = a2 - a1 => r = 4 - 7 => r = - 3

Formula :
=========
an = a1 + ( n - 1 ) x r
an = 7 + ( n - 1 ) x (-3)
an = 7 + (- 3n + 3)
an = 7 - 3n + 3
an = 7 + 3 - 3n
an = 10 - 3n


b) a 13¤ tetnos
dados :
<><><><>
a1 = 7
a2 = 4
r = a2 - a1 => r = 4 - 7 => r = - 3
n = 13

Formula :
=========
an = a1 + ( n - 1 ) x r
a13 = 7 + ( 13 - 1 ) x (-3)
a13 = 7 + (12 x (-3))
a13 = 7 + ( -36)
a13 = 7 - 36
a13 = - 29