Knowledge Base

Solution 34620: Finding the Discriminant of a Quadratic Equation Using the TI-84 Plus C Silver Edition.

How can I find the discriminant of a quadratic equation on my TI-84 Plus C Silver Edition?

The TI-84 Plus C Silver Edition does not have the built-in function to find the discriminant. However, the instructions below show how to compute the discriminant by using variables:

The discriminant is a number that can be calculated from any quadratic equation. A quadratic equation is an equation that can be written as ax² + bx + c = 0

The discriminant in a quadratic equation is found by the following formula and the discriminant provides critical information regarding the nature of the roots/solutions of any quadratic equation.
discriminant= b-4ac
Critical information on the solutions:

• When b²-4ac = 0 then there are 2 equal roots.
• When b²-4ac > 0 then there are 2 different roots.
• When b²-4ac < 0 then there are no roots at all.

Example: Find the discriminant of the equation x²+6x-5=0

• Press [1] [STO][ALPHA][A][ALPHA][:] [6] [STO][ALPHA][B][ALPHA][:] [(-)] [5] [STO][ALPHA][C]
• Press [ENTER].



• Type B²-4A*C.
• Press [ENTER] to display the discriminant. For this equation, the discriminanat is 56.



Please see the TI-84 Plus C Silver Edition guidebook for additional information.