In the quadratic formula, the expression under the square root sign, b2 - 4ac, is called the discriminant. Students will watch the video on finding the discriminant.The formula for the Discriminant. This is part of a collection of math formulas. Slope intercept form is a way to express the equation of a line and is made up of two main parts. Slope-Intercept Handout; SchoolTube - Slope Formula; Algebra. Why is this page out of focus? The discriminant is the part of the quadratic formula underneath the square root symbol: b²-4ac. Step 3: Complete the square: take the coefficient of the x term, divide it in half, and then square it. Add this to both sides of the equation.