Question

Calcule o vigesimo termo de p.a.(4,8,12)

Answer 1

o resultado é 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52, 56, 60, 64, 68, 72, 76,= 80

Answer 2

veja...

an=a20=?    a1=4     n=20      r=8-4=4

an=a1+(n-1)r
a20=4+(20-1)(4)
a20=4+(19)(4)
a20=4+76
a20=80