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Minimum and maximum
A parabola has a minimum or maximum value. Mathematically you call this in both cases the top. You can calculate the x-coordinate of the top with the formula
Explanation
A parabola is a quadratic function, that you can describe with
 = ax² + bx + c.gif){kind=small}
If the convex side points downwards, then a > 0, and the parabola has the form
The coordinates of the top can be calculated in different ways. It depends on how advanced you are in mathematics.
Quadratic formula
The x-coordinate of the top can be calculated quickly with the formula
For the intersection points of a second-degree function with the x-axis, y = 0, and thus
To calculate the zeroes x1 and x2 use the abc-formula
As a result
The x-coordinate of the summit is exactly midway between x1 and x2, and for that applies
If you substitute this in the second-degree function, you will find the y-coordinate of the top.