Given:
The price of a share of stock in JZMobile was $74 two weeks ago.
Seven weeks ago, the price was $59 a share.
To find:
The linear equation to find the price p of a share of JZMobile w weeks from now.
Solution:
Let, p be the price of a share of JZMobile w weeks from now.
The price of a share of stock in JZMobile was $74 two weeks ago. It means, the graph of linear equation passes through (2,74).
Seven weeks ago, the price was $59 a share. It means, the graph of linear equation passes through (7,59).
The graph of linear equation passes through two points (2,74) and (7,59). So, the linear equation is
[tex]y-y_1=\dfrac{y_2-y_1}{x_2-x_1}(x-x_1)[/tex]
[tex]y-74=\dfrac{59-74}{7-2}(x-2)[/tex]
[tex]y-74=\dfrac{-15}{5}(x-2)[/tex]
[tex]y-74=-3(x-2)[/tex]
[tex]y-74=-3x+6[/tex]
Adding 74 on both sides, we get
[tex]y=-3x+6+74[/tex]
[tex]y=-3x+80[/tex]
[tex]y=80-3x[/tex]
Therefore, the correct option is C.
