Respuesta :

mhanifa

Answer:

  • -704

Step-by-step explanation:

Given the sequence

  • A = -4 - 6i

To find

  • Sum of terms from i=5 to i=15

Solution

We see the sequence is AP

The required sum is

  • S₅₋₁₅ = S₁₅ - S₄

Using sum of AP formula

  • Sₙ = 1/2n(i₁ + iₙ)

Finding the required terms

  • i₁ = - 4- 6 = -10
  • i₄ = -4 -6*4 = - 28
  • i₁₅ = -4 -6*15 = -94

Getting the sum

  • S₄ = 1/2*4*(-10 - 28) = -76
  • S₁₅ = 1/2*15*(-10 - 94) = -780
  • S₅₋₁₅ = S₁₅ - S₄ = -780 - (-76) = - 704

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