Question

2. Numa PA o 8° termo é 16 e o 9° termo é 20. Calcule o 20° termo?

Answer 1

r = a₉ - a₈ = 20 - 16 = 4
a₁ = -12

an = a₁ + (n - 1) x r
a₂₀ = -12 + (20 - 1) x 4
a₂₀ = -12 + 76

a₂₀ = 64

P.A.: {-12, -8, -4, 0, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52, 56, 60, 64}