What is the explicit formula for this sequence?
-7, -4,-1, 2,
a. a^n=-7+(n-)
b. a^n=-7+(n-1)3
c. a^n=8+n(n-1)3
d. a^n=3+(n-)

The total cost of anja’s trip to the dentist was $628.35. she paid a flat fee of $89.95 which included the checkup and cleaning and then had 4 cavities filled, each of which cost the same amount. which shows the correct equation and value of x, the cost of each cavity filling?