Mia had $ 350 in her bank account at the beginning of the school year. Each week she withdraws $ 50. Two graphs model the situation

Write a function for each graph.

The correct answer is: f(x) = -50x + 350 , 0 ≤ x ≤ 7 ; f(x) = 350 – 50 ceiling(x) , 0 ≤ x ≤ 7

First graph:
Let x be the no of the weeks and y be the money in the bank account.
General equation of the line: y = mx +c
Use points (0, 350) and (7, 0).
m =  =  = -50
Putting (7,0),
0 = (-50) (7) + c
c = 350
First graph: f(x) = -50x + 350, 0 ≤ x ≤ 7
Second graph:
It is a ceiling function as can be seen in the graph.
x = 0, f(x) = 350
0 < x ≤ 1 , f(x) = 300
1 < x ≤ 2 , f(x) = 250
2 < x ≤ 3, f(x) = 200
3 < x ≤ 4 , f(x) = 150
4 < x ≤ 5 , f(x) = 100
5 < x ≤ 6 , f(x) = 50
6 < x ≤ 7, f(x) = 0
f(x) = 300 – 50 ceiling(x) + 50 = 350 – 50 ceiling(x)
Second graph: f(x) = 350 – 50 ceiling(x), 0 ≤ x ≤ 7