Find the common ratio for the following geometric sequence:
4, -12, 36, -108, 324, . . .
Enter your answer here:
-3
Right!
The student got this item correct.
-16
Sorry, that's incorrect. Perhaps you calculated the second term minus the first term. But for this geometric sequence, the difference between successive terms is not the same. For example, -12 minus 4 is -16, but 36 minus -12 is 48. The ratio between successive terms is the same, however.
The student probably confused the common ratio of a geometric sequence with the common difference of an arithemetic sequence.
432
Sorry, that's incorrect. Perhaps you calculated the fifth term minus the fourth term. But for this geometric sequence, the difference between successive terms is not the same. For example, -12 minus 4 is -16, but 36 minus -12 is 48. The ratio between successive terms is the same, however.
The student probably confused the common ratio of a geometric sequence with the common difference of an arithemetic sequence.
Sorry, that was incorrect.
The student got this item incorrect, but it is not clear why.
CommonRatio