Question

What is the summation notation for the series? 7 + 11 + 15 + ... + 203 + 207

I'm confused because my textbook says that the lower limit should be 1 and the upper limit should be 51, but earlier it said the lower limit is equal to the first term and the upper limit is equal to the last term?

Answer 1

You are being asked to write this as
\[ \sum_{i=1}^{51} (some \ expression \ involving \ i) \]

Answer 2

Hint: the expression is
ai + b
for some constants a and b.

Answer 3

\[\sum_{n = 1}^{51} ( 4n + 3)\] This is supposed to be the answer, but I thought the lower limit was supposed to be n = 7, and the upper limit should be the last term, 207? It shows that in an earlier problem.

Answer 4

Yes: when n = 1 you get the first term, 4(1) + 3 = 7
when n = 51, you get the last term 4(51) + 3 = 207

Answer 5

Oh ok that makes more sense. Thank you!