Question

How many terms of the arithmetic sequence {-4,-2, 0, ....} will give a sum of 500?

Answer 1

Answer:

a. 25

Step-by-step explanation:

Sₙ = n/2 * (2 * a₁ + (n-1) * d)

Sₙ = 500     a₁ = -4    d = 2

500 = n/2 * (-8 + (n-1) * 2) = n/2 * (-8 + 2n - 2) = n/2 * (2n - 10) = n² -5n

n² - 5n -500 = 0

(n - 25) (n + 20) = 0

n > 0

n = 25