Question

determine o 12° termo da PA ( -2,0,2..) escreva essa PA

Answer 1

an=a1+(n–1)r

an=a12
a1=–2
r=2
n=12

a12= –2 + (12-1) · 2
a12= –2 + 11 · 2
a12= –2 + 22
a12= 20

Answer 2

Encontrar a razão da PA

r = a2 - a1

r = 0 - (-2)

r = 2

an = a1 + ( n -1 ) . r

a12 = -2 + ( 12 -1 ) . 2

a12 = -2 + 11 . 2

a12 = -2 + 22

a12 = 20