.If a sequence is:
How do I prove the common difference, d, using the Arithmetic Sequence for these 2 problems?
You can't because none of these sequences is arithmetic: the first one is a (rather boring) geometric sequence with common ration = -1, and the second one is just a sequence...
a3 = a1 (n - 1)d
So would problem a be:
-2 = -2(3-1)d ?
Im getting 1/2 for d but its not the right answer