# What is a Quadratic Equation

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The word Quadratic comes from the Latin word quadratus, which literally means square. So, it is easy to guess that the equation takes the form as follows,
ax2 + bx + c
where x represents an unknown, and a, b, and c represent known numbers such that a is not equal to 0. If a = 0, then the equation is linear, not quadratic. The numbers a, b, and c are the coefficients of the equation, and may be distinguished by calling them, respectively, the quadratic coefficient, the linear coefficient and the constant or free term.
It is also called an equation of degree 2 because of the "2" on the x.
Sometimes, the equation may consist of just one or two terms like,
ax2 + bx, ax2 which are still quadratic because they still contain terms with 2nd degree.
Below you can see a graphical example of quadratic function.