You need to find the equation of a function that satisfies:
f(4)= -18
f(4)=-18
If you calculate the slope of the line using the formula:
![m=(y_2-y_1)/(x_2-x_1)](https://img.qammunity.org/2023/formulas/mathematics/high-school/78uaqhwt0aws3qfwxigaftpihnmb1gzxtp.png)
And the given ordered pairs (4,-18) and (4,-18)
![\begin{gathered} m=((-18)-(-18))/(4-4) \\ m=(-18+18)/(4-4) \\ m=(0)/(0)=0 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/1maitv5r4ha9p0qwtep56gxtnpysw8x2bn.png)
You'll determine that the slope of the line is equal to zero.
Lines with slope zero are horizontal, which means that regardless of the value of x, the value of y will remain the same.
In this case, this value is the y-coordinate of the given ordered pairs y=-18
So the equation of the line, expressed using function notation is:
![\begin{gathered} y=-18 \\ f(x)=-18 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/h9qcfo54rk2sf4x48tlbvtnfag55lq7qqs.png)