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### Introduction to the Quadratic Formula

A quadratic formula is the formula used to calculate the zeroes of a quadratic expression (or a quadratic function, or a quadratic equation). The zeroes of a quadratic functions are the two values of x at which the value of the quadratic function is zero. The quadratic formula is applicable directly if the given quadratic expression/equation/function is in the standard form. The standard form of a quadratic equation is ax^ + bx + c = 0. In this form, a and b are called the coefficients of x^2 and x respectively, whereas c is called the constant term, as it is a number. The quadratic formula is as follows:
x = (-b ± sqrt(b^2 - 4ac))/(2a)
In the above formula, ± means that you have to calculate two values of x by using the formula: one in which the + sign is used and the other in which the - sign is used.

In the quadratic formula, the part b^2 - 4ac is the most important part. It is called as the "Discriminant". It is represented by the symbol D or d. By calculating the value of the discriminant, one can know the nature of the roots of the quadratic equation before calculating them.