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.
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  [STO][ALPHA][A][ALPHA][:]  [STO][ALPHA][B][ALPHA][:] [(-)]  [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.