y = 15x + 10
Step-by-step explanation:
Given a graph, we use the equation of line y = mx + b
m = slope
b = y-intercept
First let's find the slope using the formula:
![m\text{ = }(y_2-y_1)/(x_2-x_1)](https://img.qammunity.org/2023/formulas/mathematics/high-school/sukh4lu5s7fgiz5v423o6usjd9gul4kfrj.png)
![\begin{gathered} u\sin g\text{ any two points on the line: } \\ (2,40)\text{ and (4, 70)} \\ x_1=2,y_1=40,x_2=4,y_2\text{ = }70 \\ m\text{ = slope = }(70-40)/(4-2) \\ \text{slope = }(30)/(2)\text{ = 15} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/4ro6zfoc8vu5fj0ooixzt0sf5i91rvb7ha.png)
The y-intercept is the value of y when x = 0. It is also the value of y when the line crosses the y-axis.
The value of cost when time is zero
The line crosses the y-axis at y = 10
Hence, the y-intercept is 10
The equation of line becomes:
y = 15x + 10