Answer:
Plan 1 is arithmetic and Plan 2 is geometric. Week 10 is when plan 2 exceeds the cost of plan 1.
Step-by-step explanation:
The first payment plan offers $400 each week.
1 400
2 800
3 1200
4 1600
.....
This plan is arithmetic since you add 400 for each week. Its represented by the equation y = 400x.
The second plan is $5 the first week and then doubles each week.
1 5
2 10
3 20
4 40
...
This plan is geometric since each week is multiplied by 2 for the next. It's represented by the equation y = 5(2^x).
At week 10 plan 2 becomes more expensive.
Plan 1 - y = 400(10) = 4000
Plan 2 - y = 5(2^10) = 5120