UPSKILL MATH PLUS
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Learn moreA function is of the form \(f(x) = ax^2 + bx + c\), where \(a\), \(b\) and \(c\) are constants, and \(a \neq 0\) is called a quadratic function.
Example:
![golden-gate-bridge-388917_1920.jpg](https://resources.cdn.yaclass.in/54181462-2428-45e3-986f-2082691ead72/goldengatebridge3889171920w300.jpg)
The trajectory of cables in the bridge results in a parabolic path. A parabola represents a quadratic function.
A parabola is symmetric concerning a line called the axis of symmetry. The point of intersection of the parabola and the axis of symmetry is called the vertex.
Important!
For a quadratic equation, the axis is given by \(x = \frac{-b}{2a}\) and the vertex is given by \(\left(\frac{-b}{2a}, \frac{-\Delta}{4a} \right)\) where \(\Delta = b^2 - 4ac\) is the discriminant of the quadratic equation \(ax^2 + bx + c = 0\).
A parabola usually forms a "U" shaped curve. Depending on the value of \(a\) in the general equation of the parabola \(y = ax^2\), the parabolas open upwards or downwards and vary in width.
Let us consider the simple graph \(y = x^2\).
![1.png](https://resources.cdn.yaclass.in/6f70755b-15e1-44a8-be34-54e03bccfa5b/1w400.png)
Let us compare the above graph with graphs having the higher value of \(a\).
![2.png](https://resources.cdn.yaclass.in/a8f62940-4a59-4071-b931-334b4285e292/2w400.png)
Here, the graph \(y = x^2\) is broader than the graph \(y = 8x^2\).
Similarly, compare graph \(y =x^2\) with graphs having lower values of \(a\).
![3.png](https://resources.cdn.yaclass.in/1f4057cf-47b5-4e6d-8689-8f3a2b817a63/3w400.png)
Here, the graph \(y = x^2\) is narrower than the graph \(y = \frac{1}{6}x^2\).
Important!
1. The greater the value of \(a\), the narrower is the parabola.
2. The lesser the value of \(a\), the wider is the parabola.
Reference:
https://pixabay.com/photos/golden-gate-bridge-san-francisco-388917/