Respuesta :

mhanifa

Answer:

  • 162

Step-by-step explanation:

Given AP

  • f(n)=7n - 17
  • S₉ = ?

Solution

Using formula Sₙ = 1/2n(f(1) + f(n))

  • f(1) = 7*1- 17 = -10
  • f(9) = 7*9 - 17 = 46
  • S₉ = 1/2*9*(-10 + 46) = 162