The discriminate formula is b squared minus four ac for quadratic equation in standard form ax squared plus bx plus c. In this video I'm going to talk about using What's called the discriminant to find the number of solutions to a quadratic equation.The discriminant is the part of the quadratic formula underneath the square root symbol: b²-4ac. This also tells the number of roots and whether or not the roots are real or imaginary. The discriminant won't tell you what the roots or Solutions of your quadratic equation are but they will tell you what kind of roots they are. To calculate the discriminant of a quadratic equation, the formula is b2 – 4ac.