Brand A Brand B
Brand C
40
Number
of Bags,
х
Cost ($),
35
30 +
3
24.75
The cost ($),
y, is given by
the equation
y = 7.79x,
where x is
the number
of bags.
25+
6
49.50
Cost ($)
20+
15 +
9
74.25
10
-
12
99.00
5 +
+x
1 2 3 4 5
Number of Bags
Drag the brands to order them from LEAST to GREATEST cost for 1 bag.

hello from mrbilldoesmath!

answer:

a(n) - a(n-1) -3

discussion:

this ones a bit interesting. given a(n) = 5 - 3n consider this:

a(n-1) = 5 - 3(n-1)

          = (5 - 3n) + 3             => but a(n) = 5 - 3n, the first term

          = a(n)   + 3                 => subtract 3 from both sides

a(n-1) -3 = a(n)  

or

a(n) - a(n-1) -3

you,

mrb

b.-4 units

all you   do is count how many times you move