Question

Which infinite geometric series can you NOT find the sum?

Answer 1

Answer: C) 127, 152.4, 182.88, 219.456,...

Step-by-step explanation:

You can only find the sum of an infinite geometric sequence if it converges.

One criterion to see if the series converges is if:

aₙ < aₙ₋₁

This means that, as n increases, the value of the terms decreases.

This means that as n tends to infinity, aₙ tends to zero.

Then we only can find the sum of those series where the terms are decreasing.

in A, B and D the terms are decreasing, then we can find the sum of those 3 series.

Now in the case of C, the terms are increasing, then we can not find the sum of that series.