Question

Write the sum using the summation notation assuming the suggested pattern continues 2, -10, 50, -250, +…

Is this sequence arithmetic or geometric? How do you know?

Answer 1

geometric

x=number of terms

∑ 2(-5)^(k-1)

k=1

Explanation:

the sequence has a ratio of -5 (2*-5=-10, -10*-5=50)

x=number of terms

∑ 2(-5)^(k-1)

k=1

for this i don't know what the last term is since it doesn't show in the question but just find 2(-5)^x and x will be the top term