Which of the following statements proves the series -128 + 96 - 72 + 54 - ... is geometric?

A. r = -3/4

B. r = 3/4

C. r = -4/3

D. r = 4/3

What is the explicit equation for the nth term of the arithmetic sequence 7.2, 3.8, 0.4, -3, -6.4 ...?

A. a_n = 7.2 - 3.4n

B. a_n = 7.2 + 3.4n

C. a_n = 7.2 - 3.4(n-1)

D. a_n = 7.2 + 3.4(n+1)

A jet plane has 180,000 pounds of fuel after the first hour of flight. The four engines consume a total of 15,000 pounds per hour at its cruising altitude. How many pounds of fuel remain after the 8th hour?

A. 60,000 pounds

B. 75,000 pounds

C. 120,000 pounds

D. 285,000 pounds

Which of the following equations describes the nth term for the sequence 2/3, 1/3, 1/6, 1/12, ...?

A. a_n = 2/3(1/2)^n-1

B. a_n = 2/3(1/2)^n

C. a_n = 1/2(2/3)^n-1

D. a_n = 1/2(2/3)^n