The value obtained from the subtraction of square of the coefficient of first degree term from four times the product of coefficients of second degree and zero degree terms of a quadratic equation is called the discriminant of a quadratic equation.
For example, $ax^2+bx+c = 0$ is a quadratic equation in standard form and it is formed by three unlike terms.
The value obtained from $b^2 \,–4ac$ is called the discriminant of the second degree polynomial $ax^2+bx+c = 0$.
The discriminant of a quadratic equation is denoted by either $D$ or $\Delta$ in mathematics.
$D = b^2 \,–4ac \,\,\,$ (or) $\,\,\, \Delta = b^2 \,–4ac$
$2x^2+3x+7 = 0$ is a quadratic equation.
Compare this quadratic equation with standard form quadratic equation. Therefore $a = 2$, $b = 3$ and $c = 7$.
Discriminant of this quadratic equation is $\Delta = 3^2 \,–4 \times 2 \times 7$
$\Delta = 9 -56 = -47$
Therefore, the discriminant of the quadratic equation $2x^2+3x+7 = 0$ is $-47$.