Example 4: Applying the quadratic formula | Quadratic equations | Algebra I | Khan Academy

Application Problem with Quadratic Formula

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[EmmysCoolVids]

I have a test tomorrow I still don't get any of this

[davidchillton]

When are you ever going to use this in real life ? Unless it's for your job.

[likwah]

My teacher apparently estimates each week's assignments to be 1.5-2 hours a week. They literally take 3-5 if you actually try hard enough. Actually even more

[sagestopmotions]

Thanks SOO much!! This was SO helpful for studying!

[clashofclansdogdowlers]

can you make more application word problems? using that formula?

[PatrickCraig-lhis]

I noticed a lot of people asking where the -16 comes from. This particular variation of the quadratic is a _physics_ formula, h(t) = -1/2 * g * t^2 + v0 * t + h0, where h(t) is height as a function of time, g is the acceleration due to gravity on Earth (9.8 m/s^2 or 32 ft/s^2), v0 (pronounced "vee naught") is the initial upward velocity in feet per second, and h0 (pronounced "aych naught") is the initial height of the projectile above the ground. 32 * (-1/2) yields -16, which becomes the coefficient for the t^2 term. And yes, if you're on Earth (and using English units instead of metric), -16 will _always_ be the coefficient of that first term. I hope this helps for future viewers.

[ry]

Kahn Academy. You have caused me so much pain and suffering in the math department. 😭

[moki]

Why is positive 4 it should be negative right if you multiply -8 times -25 the product is 200 times negative 4


The quadratic b2-4(a)(c)

[julietacortese]

isn't it faster to use the d= r.t formula? (distance = range(speed).time) We are given distance 50 and speed 20 ft/s, so it's 50=20t, now we just flip it to 50/20 = t and simplifying it its 5/2

[chocolateshmurda]

I had to finish a take home assessment and this helped a lot man, thanks. I fucking hate algebra

[MidnaTriforce]

im confused on how to this when your discriminant is negative though -____-

[BobBob-uvfq]

Really useful, more example like this would be great

[BobBob-uvfq]

It really is very easy when one knows the system

[ecaj]

What if you get positive answers for both x-intercepts? Then which one do I have to choose as an answer?

[blessysagmit]

Me rn;


How you like that?


Guys! Can you teach me how to solve this lesson? Huhu

[javierrod]

How would this work if solving for an percentage and a specific year equation?

[carrevenger]

Why didn’t you use the simplified equation when confirming that h is zero at the end? Is it not allowed or something?

[dirkfield]

is he writing on the computer or on a pen to computer image software?

[engr.tonystark]

Hmmm...I'm in AP Physics C, this is a kinematics problem.

[tylercheek]

Ok it's all good until you changed the equation by multiplying 2. I don't get it.