The discriminant is the part of the quadratic formula underneath the square root symbol: b²-4ac. The discriminant tells us whether there are two solutions, one solution, or no solutions.

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drossington

7 years agoPosted 7 years ago. Direct link to drossington's post “Why do we need the discri...”

Why do we need the discriminant? We already know what kind of solutions there are when we solve using the quadratic formula.

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(8 votes)

Jerry Nilsson

7 years agoPosted 7 years ago. Direct link to Jerry Nilsson's post “𝑎𝑥² + 𝑏𝑥 + 𝑐 = 0 ⇒ �...”

𝑎𝑥² + 𝑏𝑥 + 𝑐 = 0 ⇒ 𝑥 = (-𝑏 ± √(𝑏² – 4𝑎𝑐))/(2𝑎)

Using this formula, it is advisable to calculate the discriminant, 𝑏² – 4𝑎𝑐, first because if it is negative we know that there are no real solutions and we can skip the rest of the calculations.

(108 votes)

Shuss824

7 years agoPosted 7 years ago. Direct link to Shuss824's post “"A discriminant of zero i...”

"A discriminant of zero indicates that the quadratic has a repeated real number solution." what exactly does this mean?

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(20 votes)

FightingJ

6 years agoPosted 6 years ago. Direct link to FightingJ's post “It means that you only ha...”

It means that you only have one solution

(37 votes)

Kathy Downey

7 years agoPosted 7 years ago. Direct link to Kathy Downey's post “I don't understand what F...”

I don't understand what F(x) means? The f symbol just appeared

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(0 votes)

David Severin

7 years agoPosted 7 years ago. Direct link to David Severin's post “f(x) is read as f of x, a...”

f(x) is read as f of x, and it means a function in terms of x. This is called functional notation, and it has the same meaning as y = at this point in math. As you get into Algebra II, you will learn how to combine functions where this language will be more useful than the y = form of equations. The biggest use of f(x) in Algebra I is when you are asked to find a specific value of x. So if f(x) = 2x + 6, this is equivalent to y = 2x+ 6, but if I wanted to find the value of the function at x = 8, with functional notation, I could just say f(8) which is solved by putting 8 into x and getting f(8) = 22.

(42 votes)

westina_7

5 years agoPosted 5 years ago. Direct link to westina_7's post “how can the discriminant ...”

how can the discriminant help graph?

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(3 votes)

Isabella C

5 years agoPosted 5 years ago. Direct link to Isabella C's post “It determines the number ...”

It determines the number of times the graph crosses the x-axis.

Discriminant > 0: the graph crosses the x-axis twice

Discriminant = 0: the graph touches the x-axis at its maximum or minimum point

Discriminant < 0: The graph has no x-intercepts, which means it is wholly above or below the x-axis(18 votes)

Sage

4 years agoPosted 4 years ago. Direct link to Sage's post “How do you find the discr...”

How do you find the discriminant from looking at a graph?

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(2 votes)

Hannah Alisse

4 years agoPosted 4 years ago. Direct link to Hannah Alisse's post “I don't think there's an ...”

I don't think there's an easy way to find the exact value of the discriminant by looking at the graph, but looking at the graph can tell you if the discriminant is positive, negative, or zero.

If the graph doesn't touch the x axis at all, the discriminant is negative

If the graph touches the x axis a only one point, the discriminant is zero

If the graph touches the x axis at two distinct points, the discriminant is positive.Sorry I couldn't give you an easy answer, but if you know the equation, then it's pretty easy to find the discriminant, so I don't know if it's worth it to learn how to find it from only the graph.

(18 votes)

Anirudh Parmar

6 years agoPosted 6 years ago. Direct link to Anirudh Parmar's post “if the eqaution has no re...”

if the eqaution has no real roots , use the discriminant to determine the value of n.

0=5.5x^2+nx+n and the discriminant is -40.This is another homework question I dont know how to do this.

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(4 votes)

rylan.wetsell

2 years agoPosted 2 years ago. Direct link to rylan.wetsell's post “basically you're looking ...”

basically you're looking b and c, which in this case are the same, so you can plug everything into the discriminant equation (b^2 -4ac):

n^2 -4(5.5)(n)=-40

i don't know if i'm being dumb and there's an easier way to solve this but you can simplify this to:

n^2 -11n +40 =0

which, you'll notice, is a quadratic equation, so you just solve for that to get n.(1 vote)

sunix777

7 years agoPosted 7 years ago. Direct link to sunix777's post “How is a quadratic equati...”

How is a quadratic equation with a negative discriminant graphed?

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(3 votes)

Kim Seidel

7 years agoPosted 7 years ago. Direct link to Kim Seidel's post “You just don't have x-int...”

You just don't have x-intercepts to work with.

You can graph it using a table of values -- pick values for X and calculate Y for each X.

You can still find the vertex and axis of symmetry.(13 votes)

Radha Krishna

a year agoPosted a year ago. Direct link to Radha Krishna's post “how discriminant decides ...”

how discriminant decides what are the nature of the two roots?

I mean how?•

(1 vote)

Kim Seidel

a year agoPosted a year ago. Direct link to Kim Seidel's post “The quadratic formula: x ...”

The quadratic formula: x = [-B +/- sqrt(B^2-4AC)] / (2A)

The discriminant is B^2-4AC. Notice this is the portion of the formula inside the square root.If the discriminant = 0, then the formula degrades to x = -B/(2A). So, there is only one solution.

If the discriminant is positive, then the square root creates a real number. So, there are 2 real solutions.

If the discriminant is negative, then the square root is not a real number. Square roots of negative values require the using of complex numbers. So, there are 2 solutions, that are not real numbers. Or, 2 complex solutions.

Hope this helps.

(16 votes)

jpalacios2023

a year agoPosted a year ago. Direct link to jpalacios2023's post “I quite literally got 100...”

I quite literally got 100% mastery on everything for this section a week ago, yet I log on today to do a review and I don’t remember anything?! Is my memory just bad?

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(5 votes)

Faerie

9 months agoPosted 9 months ago. Direct link to Faerie's post “If it helps, you can try ...”

If it helps, you can try writing down the key information, and looking for practice sheets to complete so you can drill the methods in your head. Personally, I'll do the practices on here multiple times before moving on.

(3 votes)

Bree

4 years agoPosted 4 years ago. Direct link to Bree's post “I have a question that wa...”

I have a question that was given to me in class, it is:

x^2 - (k+4)x + k + 7 = 0. Find k.

Answer: k = -6 & 2I understand HOW to put this into the discriminant and get the correct answer, but not WHY we do that. How come we have to use the discriminant to find k? How do I know when I need to use this for equations?

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(3 votes)

Timo

4 years agoPosted 4 years ago. Direct link to Timo's post “The answers that you foun...”

The answers that you found (for k) are when the discriminant equal 0 (b^2-4ac=0) -- which means that the function has only one solution.

**When you graph**(k+4)^2-4(k+7), you get a convex parabola with vertex (-2,-16) and x-intercepts at (-6,0) and (2,0).**That implies**that for k; -6<k<2, that the discriminant is negative. In other words there is no real solution for those values of k.

For k=-6 & k=2, which you found the function (with x) has only one x-intercept (which is the vertex).

For k<-6 & k>2, the function has two solutions (x-intercepts).**So**, you find the discriminant in order to figure out for which values for k, the function has 0, 1 or 2 solutions.(6 votes)