Why quadratic equations are used in real life?

As you have seen in the previous examples quadratic equations are everywhere, but you may now think.. Why do I need quadratic equations, who ever is gonna want to crate an equation for the MC Donald's signboard ? But my answer my dear all is.. Quadratic Equations are essential if you want to create a bridge and before reproduce it's shape in a Cartesian plan, if you are asked to create something you will first need to plot it and then create it real and in order to do this you need the quadratic equation formula. We also have to remember that algebra is essential for the discovery of many things and that its one of the biggest representations of maths.