Answer:
The equation of the parabola is 
.
Step-by-step explanation:
Since the directrix is of the form 
, the parabola is vertical. The vertex of the parabola (
) is the midpoint between the focus (
) and a point of the directrix (
), that is to say:
(1)
If we know that 
and 
, then the coordinates of the vertex of the parabola:
The vertex factor (
) is the distance of the focus with respect to the vertex:
![p = \sqrt{[F(x,y)-V(x,y)]\,\bullet \,[F(x,y)-V(x,y)]}](https://tex.z-dn.net/?f=p%20%3D%20%5Csqrt%7B%5BF%28x%2Cy%29-V%28x%2Cy%29%5D%5C%2C%5Cbullet%20%5C%2C%5BF%28x%2Cy%29-V%28x%2Cy%29%5D%7D)
(2)
If we know that and , then the vertex factor is:
The equation of the parabola in the vertex form is described below:
(3)
Where:
- Independent variable.
- Dependent variable.
- Coordinates of the vertex.
If we know that 
and , then the equation of the parabola is .
It's the bottom one. 20 dollars has to be less than or equal to the amount. you cannot spend more than $20
