Answer: {2, -2, -6, -10}
Arithmetic sequences are defined by a common difference between the numbers that’s both constant and consecutive.
To break it down:
The first option is {-1, 3, -3, -1}, which appears to be alternating, and there is more than 1 difference between the n term values. That is:
-1 to 3 = increase of 4
3 to -3 = decrease of 6
-3 to -1 = increase of 2
Therefore does not follow the definition of an arithmetic sequence.
The second option (the answer) {2, -2, -6, -10} is arithmetic, as it consistently and thus consecutively decreases by 4.
Finally, the last two sequences have the same issue with their pattern, {3, 6, 9, 15}
and {4, 14, 24, 32}. In which they stay constant for the first three n terms, but suddenly change in value on the 4th n term. Therefore, they are not arithmetic.
I hope this helped!
Ok, so the question is based on geometric progression. Remember, the formula for calculating the nth-term of a geometric progression is:
. The a in the expression stands for the 1st term of the sequence, and r is the common ratio of the elements of the sequence. Now let's take a look at the problem.
"A ping pong ball has a 75% rebound ration". We can infer that our common ratio, r, is 75% which is 0.75.
"When you drop it from a height of k feet...", this means the first height you drop it from, a.k.a, the first term.
Now going back to the expression, the nth-term =
, we can substitute our common ration, 0.75 with r, and our 1st term, k, with a. This becomes:
. This becomes our expression.
a. The highest height achieved by the ball after six bounces. Our nth-term here is 6, so let's use our expression to find the 6th term. 
b. The total distance travelled by the ball when it strikes the ground for the 12th time. This involves the use of the sum of elements in the geometric progression. The formula for that is
, provided that r is less than 1, which it is in this case, since 0.75 is less than one. Our nth-term here is 12, so we substitute.

(c+3)-2c-(1-3c)=2
c+3-2c-1+3c=2
2c+2=2
2c=0
c=0