I'm assuming that you mean
because if you meant
then u would simplify and you couldn't make it the subject.
Under this assumption, we start with
We multiply both sides by
We expand the left hand side:
We move all terms involving u to the left and all terms not involving u to the right:
We factor u on the left hand side:
We divide both sides by
Try this solution, it consists of two parts (MN=8).
True. A series is arithmetic if its terms come from an arithmetic sequence.
And a sequence is said to be arithmetic any of its two consecutive terms differ by a fixed difference, common to any consecutive pair.
As you can see, in this case, all terms differ by 2, so the sequence
is arithmetic, and thus the series
is arithmetic as well.