Answer:
![y=45x+40](https://tex.z-dn.net/?f=y%3D45x%2B40)
Step-by-step explanation:
Let
x -----> the number of days
y ----> the total cost in dollars,
we know that
The equation of a linear function in slope intercept form is equal to
![y=mx+b](https://tex.z-dn.net/?f=y%3Dmx%2Bb)
where
m is the slope o rate of the linear equation
b is the y-coordinate of the y-intercept
Remember that the y-intercept is the value of y when the value of x is equal to zero
In this problem we have
The slope is equal to the rental cost per day
so
![m=45\frac{\$}{day}](https://tex.z-dn.net/?f=m%3D45%5Cfrac%7B%5C%24%7D%7Bday%7D)
When the number of days is equal to zero (x=0) the total cost is equal to $40 (administrative fee for the cleaning and maintenance of the car)
The y-intercept is the point (0,40)
so
![b=\$40](https://tex.z-dn.net/?f=b%3D%5C%2440)
substitute the values
![y=45x+40](https://tex.z-dn.net/?f=y%3D45x%2B40)