Hello, Ranger SVO!

You're curious . . . good for you!

While playing with parabolas in college (centuries ago),

. . I "discovered" some facts that might help you.

Code:

* | */
| /
* | *P(x,y)
* | */
---------***---o----------
| /↑
| /(½x,0)
| /
|/
o ←(0,-y)
/|

Given the parabola: . , the tangent at point

. . has an x-intercept of and a y-intercept of

The tangent at always has a point directly below the vertex

. . with the same vertical displacement (only downward).

Your parabola has its vertex at

Your point is 4 units *above* the level of the vertex.

Hence, it has a point 4 units directly *below* the vertex:

Now you can write the equation through and