Write the explicit formula for the geometric sequence.

a1 = -5 a2 = 20 a3 = -80

a. an = -5 • (-4)n

b. an = -5(-4)n-1

c. an = -4(-5)n-1

d. an = -5 • (4)n

Identify all the cases where non-probability sampling is used when attempting to study the characteristics of a large city. studies on every subject in the population divide a population in groups and obtain a sample studies with a limited amount of time demonstrate existing traits in a population studies with the nth person selected

Twice the sum of a number and 2 is equal to three times the difference of the number and 8. find the number.

Provide all steps given to find the answer. simplify: 5(2x+9)²