Question

Dada a PA (-10,0,10,20, ..), calcule : a soma dos dez primeiros termos dessa PA

Answer 1

(-10, 0, 10, 20, ...)

a₁ = -10

r = 20 - 10 ---- r = 10

a₁₀ =  a₁ + (10 - 1) . 10 ------ a₁₀ = -10 + 9 . 10 ---- a₁₀ = -10 + 90 --- a₁₀ = 80

S₁₀ = (a₁ + a₁₀) . 10/2 ----- S₁₀ = (- 10 + 80) . 5 ---- S₁₀ = 70 . 5 ----S₁₀ = 350