Like what you saw?
Create FREE Account and:
 Watch all FREE content in 21 subjects(388 videos for 23 hours)
 FREE advice on how to get better grades at school from an expert
 FREE study tips and eBooks on various topics
The Discriminant  Concept
Alissa Fong
Alissa Fong
MA, Stanford University
Teaching in the San Francisco Bay Area
Alissa is currently a teacher in the San Francisco Bay Area and Brightstorm users love her clear, concise explanations of tough concepts
The discriminant is the term underneath the square root in the quadratic formula and tells us the number of solutions to a quadratic equation. If the discriminant is positive, we know that we have 2 solutions. If it is negative, there are no solutions and if the discriminant is equal to zero, we have one solution. The discriminant is calculuated by squaring the "b" term and subtracting 4 times the "a" term times the "c" term.
The discriminant is a really handy tool when you think you're getting a weird answer. Here's why. The discriminant tells you how many solutions there are to quadratic equation or how many x intercepts there are for a parabola. It doesn't tell you what those numbers are like what the x intercept values are, it just tells you how many of them there should be. And it sounds like that's not useful but it actually is especially when you're checking your work.
So here is what it looks like. The discriminant is the formula b squared minus 4ac remembering that a, b and c are the coefficients of your quadratic in standard form. It tells you the number of solutions to a quadratic equation. If the discriminant is greater than zero, there are two solutions. If the discriminant is less than zero, there are no solutions and if the discriminant is equal to zero, there is one solution.
This is something you just kind of have to memorize. It goes hand in hand with the quadratic formula. So if you guys have learned that, this will make a lot of sense. If you haven't learnt the quadratic formula yet you'll probably learn it tomorrow in math class. Just know that, what you're looking at is whether or not b squared minus 4ac is greater than zero, less than zero or equal to zero. And it tells me how many answers I should have. It doesn't tell me what the answers are just how many of them I should have in order to get the problem correct.
Please enter your name.
Are you sure you want to delete this comment?
Alissa Fong
M.A. in Secondary Mathematics, Stanford University
B.S., Stanford University
Alissa has a quirky sense of humor and a relatable personality that make it easy for students to pay attention and understand the material. She has all the math tips and tricks students are looking for.
Your tutorials are good and you have a personality as well. I hope you have more advanced college level stuff, because I like the way you teach.”
Thanks alot for such great lectures... I never found learning this easier ever before... keep up the great work.... :)”
You seem so kind, it's awesome. Easier to learn from people who seem to be rooting for ya!' thanks”
Concept (1)
Sample Problems (5)
Need help with a problem?
Watch expert teachers solve similar problems.

The Discriminant
Problem 1 4,723 viewsFind the number of solutions of
3x² − 2x = 7 
The Discriminant
Problem 2 3,728 viewsA furniture business uses the formula f(x) = 5400 + 300x − 40x² to calculate its monthly income, where f(x) stands for income and x represents the number of items sold. Will their monthly income ever reach $6000?

The Discriminant
Problem 3 848 views 
The Discriminant
Problem 4 587 views 
The Discriminant
Problem 5 577 views
Comments (1)
Please Sign in or Sign up to add your comment.
·
Delete
Nimo · 6 months ago
extremely nice video...