1. In mathematics, triangle is Delta, which is the pronunciation of the fourth Greek letter. Its capital is δ and lowercase is δ. In mathematics or physics, the capitalized δ is used to represent the incremental symbol. And lowercase δ is usually used to represent variables or symbols in higher mathematics. In algebra, δ is used as a discriminant to represent the root of a quadratic equation with one variable. That is, δ = B2-4ac.

2. The discriminant of roots is a formula for judging the number of real roots of an equation, which is widely used in solving problems, involving the range of solution coefficients, judging the number and distribution of roots of an equation, etc. The discriminant of the root of the unary quadratic equation ax 2+bx+c = 0 (a ≠ 0) is b 2-4ac, which is expressed by "δ" (pronounced as "δ").