I'm guessing the sum is supposed to be

Split the summand into partial fractions:


If
, then

If
, then

This means

Consider the
th partial sum of the series:

The sum telescopes so that

and as
, the second term vanishes and leaves us with

I’ll assume the c is b. (1/2) x (5) x (2) x (2) is 10
Answer:
Step-by-step explanation:
2⅝ miles/(3½ minutes) = (21/8 miles)/(7/2 minutes) = ¾ mile/minute
d = ¾m = 0.75m
Yes it is a geometric sequence and the common ratio is 2/3