An **equation of 2nd degree** is called quadratic equation. In more detail, the quadratic equation is an equation, which contains the square of the unknown (variable) quantity, but no higher power.

### General or standard form of a quadratic equation:

It is a 2nd degree equation in one variable x of the form as below,

where a ≠ 0 and a, b, c are real numbers.

Here, a is the co-efficient of x^{2}, b is the co-efficient of x and c is constant.

If b = 0 in a quadratic equation *ax ^{2} + bx + c = 0*, then

*ax*is called a

^{2}+ c = 0**pure quadratic**equation.

**Note:** If a = 0 in *ax ^{2} + bx + c = 0*, then it reduces to a

**linear equation**

*bx + c = 0*

### Examples:

*x ^{2} – 7x + 6 = 0 *(quadratic equation, standard form)

*3x ^{2} + 4x = 5 *(quadratic equation, not in standard form)

*x ^{2} – 16 = 0 *(pure quadratic equation)

*4x ^{2} = 7 *(pure quadratic equation)