this formula, doesn't rely on a product, relies on a "sum", or is namely an arithmetic sequence, aₙ₋₁ -3 is another way of saying, the value of the previous term minus 3, so it relies on the ordinal value of a term, so is an recursive formula, well, let's get it when n = 4.
Slope of the line J
(6-1) / (-3-(-6))
5 / 3
so
m = 5/3
If this line passes through (15,-1)
y = mx + c
-1 = (5/3)*15 + c
-1 = 25 + c
c = -26
equation is
y = (5/3)x - 26
It depends if the 12 spice jars are all different.
If they are:
_ _ _ _ _ _ _ _ _ (9 spaces)
12*11*10*9*8*7*6*5*4
12 possibilities for first one, 11 for second, etc...
Multiply out to get:
79833600
Well, it goes 5 inches per second so after 4 seconds it is 4 times 5 =20 inches under the surface, add that to 5 feet and you get 6 ft and 8 inches