Solving a quadratic by factoring | Quadratic equations | Algebra I

Solving a quadratic by factoring | Quadratic equations | Algebra I | Khan Academy

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17 жыл бұрын

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Factoring quadratics
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Algebra I on Khan Academy: Algebra is the language through which we describe patterns. Think of it as a shorthand, of sorts. As opposed to having to do something over and over again, algebra gives you a simple way to express that repetitive process. It's also seen as a "gatekeeper" subject. Once you achieve an understanding of algebra, the higher-level math subjects become accessible to you. Without it, it's impossible to move forward. It's used by people with lots of different jobs, like carpentry, engineering, and fashion design. In these tutorials, we'll cover a lot of ground. Some of the topics include linear equations, linear inequalities, linear functions, systems of equations, factoring expressions, quadratic expressions, exponents, functions, and ratios.
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Пікірлер: 174

@jennymathews4292 4 жыл бұрын

This was uploaded when I was two, now I’m a freshman. Crazy.

@lali2955 3 жыл бұрын

And now you're a sophomore.

@Itsbilaa_55 3 жыл бұрын

Hehe I think we're almost the same age

@BasicRock123 3 жыл бұрын

Crazy how these videos hold up 14 years later

@jennymathews4292 3 жыл бұрын

@@lali2955 Yep, crazy. I still think back to this doing Pre-Calc now lol

@mask1776 3 жыл бұрын

lol this was made 1 year before I was born

@coolkid5850 6 жыл бұрын

This video was uploaded when i was three now im a freshman

@broganshirazi3706 4 жыл бұрын

yo same except im a sophmore now

@justyndeschenes7959 4 жыл бұрын

Same

@svian2 3 жыл бұрын

@@broganshirazi3706 same

@svian2 3 жыл бұрын

Sophomore

@turmoilbreaker9301 3 жыл бұрын

how was grad?

@jadealex2190 9 жыл бұрын

Thank you so much my teachers were making this so confusing for me but now I get it!

@mimilizzi97 12 жыл бұрын

This video is way better than the other videos on this subject from Khan Academy. I watched the other videos about 4 times trying to understand the concept, before i found this one. As soon as i saw this one, I watched it, and understood it right away.

@HybridBoarders 12 жыл бұрын

This helped me out a lot i wish i found it sooner

@KswolfVideos 12 жыл бұрын

I've been trying to learn how to factor for several weeks. I just learned how in nine minutes.

@maryjanesbaby9392 4 жыл бұрын

Behold the Pale Horse Me too!

@hotcopone 14 жыл бұрын

hi thanks for the video. it really helps.. 1 thing tho. i recommend u should get those digital pen mouse things. its alot easier to write with and makes it alot clearer. thanks anyway... :)

@tbrew222 10 жыл бұрын

Wow this video is so old... It was uploaded when I was in 3rd grade, and now I'm a sophomore

@sarahkabir3683 9 жыл бұрын

!! same here i was actually in the 2nd grade and its quite mind-blowing to think of it.

@tbrew222 9 жыл бұрын

***** lol ya I didn't even know he made videos back then

@davidhovis2513 6 жыл бұрын

Exactly the same lol

@Rafakookoo 6 жыл бұрын

Lol your comment was 4 years ago and I am now a sophomore, time flies!

@geobrizuela 6 жыл бұрын

SAME haha

@YIJ_0 3 жыл бұрын

This guy has been doing this before I was born, he needs a raise

@kendallpressley3825 11 жыл бұрын

This has helped me out so much, I wish I would have found it sooner!

@soopi49 13 жыл бұрын

Thanks very much Khan, this is really great and easy to follow.

@mateomarangelli9191 8 жыл бұрын

You want to know something sad? Last year, I was in Eighth Grade. I had Algebra 1 as the math course. (Because CPS does that now) My math teacher was awful. I learned absolutely nothing the whole year. You want to know something even sadder? This year, I am a freshman in High School. My math class is Honors Geometry 1. I received a High Pass on my algebra exit exam. I have no idea how. In H Geometry, we build off of stuff learned in A1. Stuff I didn't learn. I am screwed.

@slavsquatsuperstar 8 жыл бұрын

+Mateo Marangelli NOW WAY!

@flyingmonkey2459 8 жыл бұрын

+Mateo Marangelli story of my life

@TrackieType 8 жыл бұрын

+Mateo Marangelli Yeah, I'm in the middle of Eighth Grade right now. Teacher is horrible, I just learn the general topics and then just look up the actual subjects on Khan Academy. It is kind of sad, because I am recommended for AP Geometry next year.

@CreatedbyLeon 7 жыл бұрын

You're obviously good at math you just have to find someway to like the subject relate it to real life. Remember math is a skill, the more you do it the better you get at it.

@CreatedbyLeon 7 жыл бұрын

Reilitas true we get an overload of teachers who don't like their jobs or pay so they dont teach students anything. I'm currently in a catch up class at a CC and they put little to no effort in teaching the material mostly everything I learned I taught my self online or through books at stores. If I depended on the teachers I wouldn't pass.

@neongalaxy9976 6 ай бұрын

This is older than me! And it’s teaching me lmao. Great video for people with bad teachers, like me

@YdLeet 15 жыл бұрын

Thanks ever so much Salman! :)

@Someone-gb8nf 3 жыл бұрын

This video was uploaded when I was one month and 13 days old. I am a freshman now.

@ChefKekeMartialArts Жыл бұрын

Dang this video was made before i was born now im watching it because of math class in Grade 9 💀

@themanunderurbed 9 жыл бұрын

Thanks this helps so much!

@noahjoo7231 3 жыл бұрын

the quality of this video is just *chefs kiss*

@cool6936 12 жыл бұрын

Awesome video, what i dont get though is that when you sketched the parabola the two x points would be positive however when you worked it out they were negative....

@runeslayerisawsome 6 жыл бұрын

MATH PAPA

@MCPhantomX 6 жыл бұрын

lol it wants me to pay money now...

@summeriswandering628 3 жыл бұрын

wow i was 2 when this was uploaded and now i’m almost a senior.

@aksiadilet-sultan3321 3 жыл бұрын

This video was uploaded a month before I was born and now it is saving my life as a freshman

@HuntersWar 11 жыл бұрын

Helped alot thx

@ronjansenmenor8147 8 жыл бұрын

thank you khan academy learning has been so easy, and easy to watch because it only 240P but still readable and so fast to load

@KeyurKumbhare 7 жыл бұрын

notes2revise.blogspot.in/2017/03/algebra-khan-academy-notes-coming-soon.html

@lpoiuy341 13 жыл бұрын

There is a book that only works with Algebra. I use this book while learning from this amazing teacher. It's called Effortless Algebra. This book shows step by step how to do algebra. I suggest to you all to get this book. It helps me a lot.

@theforgottenbook7775 10 ай бұрын

You came down from heaven to help me study 😢

@MovieMad007 13 жыл бұрын

god if only I had this when i was at school I'd have been the top of the class!! Am 38 now and did my GCSE in summer of 86! The books that are around now like the "Dummies" series - eeesh I only wish I had these back then!

@suckmyloli 16 жыл бұрын

As far as I know the FOIL method refers to when the question is in the form of eg. (x-2)(x+4) and you need to get it to an equation you can solve using the methds in the vid. So in this case you would get x^2+4x-2x-8 then you tidy it up x^2+2x-8=0 and from here you can factorise to find the roots.

@SamRobertduty 16 жыл бұрын

Thank you !

@camcam1690 3 жыл бұрын

this was uploaded a couple months after i was born, now im freshman

@GabrielEze 5 жыл бұрын

Great video. You should also mention somewhere that solving a quadratic equation by factoring works only when the coefficient of x^2 is equals 1. That means when the coefficient of x^2 is NOT equals 1, and you're not able to divide across in a way that does not results in having a fraction anywhere in the equation, this method does not work. In that case, you will have to use the quadratic formula method or "completing the square" method. I know this is an old video, you could include this in the description section. Thanks for sharing

@teaganmckay8706 4 жыл бұрын

I feel like he did mention that when he divided 2x² by 2 in the second example problem. Although perhaps he could have put more emphasis on you having to do so for the problem to work.

@venkats1630 11 жыл бұрын

Can u do a series of videos on parabolas because they seem a little confusing to me

@autumndockery441 5 жыл бұрын

What if the two terms that we were factoring were not able to be evenly divided by two. How would you factor out once the big number was out of the way?

@josejimenaz 9 ай бұрын

So much nostalgia at my college years

@WhatTheShizzzzz 12 жыл бұрын

better than my teacher

@gasmaskguys4965 12 жыл бұрын

very detailed (Y)

@airfreak789854521 15 жыл бұрын

excellent job man! 100X better than my lame teacher and the textbook put together! xD

@angle4everr 15 жыл бұрын

Can u plaese put up videos on factoring polynomails and ditstrubtive property.

@jameslee-vj9ez 6 жыл бұрын

the parabola intersects the x axis at 2 and 4. when it should intersect it at -2 and -4. he graphed it first.

@AsEOfSp8dES14 15 жыл бұрын

bluemicrowave is right, the parabola is on the wring side of the y-axis but that wasnt bad for an estimate

@Sammyshots 3 жыл бұрын

This video was uploaded when I was 4 months, now I'm a freshman

@234234234mr 13 жыл бұрын

@bolmung that was just an example of what one looks like in the beginning.

@xKINGkhanSRKx 12 жыл бұрын

you factored the 2 out at the starting, does that 2 just leave the equation now?

@1Otnt4354g Жыл бұрын

this video uploaded before I was born

@rajeanam7976 5 жыл бұрын

This video was made when I was four months old

@akerraahito7855 8 жыл бұрын

how did you get -4 ?

@NotTheBestPvP 8 жыл бұрын

I'm wondering the same thing!

@alvifani 8 жыл бұрын

If u re talkin about the first problem, he found it as One OF the number u need the Make the equation equals zero. For instance : (x+4)=0, x must be equal -4 to satisfy the equation

@NotTheBestPvP 8 жыл бұрын

Thank you very much, didn't even realize that!

@backlikevertabrae 13 жыл бұрын

@dmiv424 So true, they always complicate things so much.

@BlancoPushP 4 жыл бұрын

This was uploaded when I was 2 now I’m a sophomore

@damarissamora8299 4 жыл бұрын

This Was Made the year i was born now im in 8th grade

@Deathless2288 15 жыл бұрын

it should be x = (-b +/- sqrt (b^2 - 4ac)) / 2a

@slavsquatsuperstar 8 жыл бұрын

I was told never to divide, only factor out the 2

@idster7 14 жыл бұрын

is there any way to get the answers algebraically starting with A+B=-1 and AxB=-30??

@SaaditKhan 14 жыл бұрын

@LancerZEV well, he took up the most of the 10 mins allowed, i dont see how he could have fit it in there, he's down a good job

@larrydeandixon8205 4 жыл бұрын

this video was uploaded when i wasnt even a year old, now im a freshman

@domigonz7094 3 жыл бұрын

This video was uploaded when I was 1, now I'm a sophomore.

@jinger1654 2 жыл бұрын

I was a 3 months at this time lol

@jerfersonmatos28 6 жыл бұрын

Equação do segundo grau?

@govamurali2309 6 жыл бұрын

Why do we set f(x) as zero??

@doctapeppamanjr 11 жыл бұрын

Whoever said that the vertical line was the y-axis? It's obviously actually the line x = -6.

@kaylad2663 4 жыл бұрын

I was 3 when this was uploaded

@bolmung 13 жыл бұрын

=( Was that parabola he drew in the beginning for the first problem just an example of what a parabola looks like? Because he got negative answers.... Would they have intersected the x axis on the negative side? Or am I not getting something? >.

@kikiscatto4826 3 жыл бұрын

This video was uploaded when I was one I am a sophomore now

@wonton55923 11 жыл бұрын

but how do you foil?

@fivemeomedia 10 жыл бұрын

i wish you could of explained what a parabola was first :/

@gamerdio2503 6 жыл бұрын

miguel look at a graph of X^2. That's a parabola

@epbrennan0746 3 жыл бұрын

I was -1 when this was uploaded. Now I’m in 8th grade

@alyssaandalexis42 9 жыл бұрын

Your zeros equal -2 and -4 but you graphed it on 2 and 4. Am I missing something?

@alvifani 8 жыл бұрын

Yes he did wrong in fact, by the Way not for purpose i guess. In the prospective OF the cartesian plane the parabola should have intersect the negative x axis

@skittlegamingpg4145 2 жыл бұрын

do you think next time you could make the audio a little bit lower

@joshavery 9 жыл бұрын

What if there is no c term

@sxcrekt6437 9 жыл бұрын

It is 0

@lisinka3 15 жыл бұрын

At your website, in the solving a quadratic by factoring module it spit out a problem of the type. f(x)=-9x2+441 I can't find how you would solve this in the video, and it doesn't give a hint. Can somebody help me out? (Answer is supposed to be x=7,7)

@SaaditKhan 14 жыл бұрын

@LancerZEV wooow, sorry I didn't know that you were the grammar police

@gracegilbert1666 3 жыл бұрын

This video was uploaded when I was two months old and now I’m a sophomore

@shootingstars2127 5 жыл бұрын

so wait can there be no x intercepts on a parabolic graph

@SaaditKhan 14 жыл бұрын

@LancerZEV wooow, sorry, I didn't know that you were the grammar.

@ray-without-organs 3 ай бұрын

this video was made when i was -4, now im 14

@Nick-qc7wm 3 жыл бұрын

i was 3 months old when this was made lol.

@jinger1654 2 жыл бұрын

Samee

@valdas0 13 жыл бұрын

@RollsRoyceMr yes, his graph is wrong. Parabola should cross the x-axis at -2 and -4.

@SaaditKhan 14 жыл бұрын

@LancerZEV I didn't realize that missing one letter would cause you to "decipher" it... I think it's pretty obvious what I meant.

@i1equ 3 жыл бұрын

this video was uploaded when I wasnt even born lmfao im in eighth grade

@ahmedhasan3136 8 жыл бұрын

why is fx equal to zero when parabola intersects x_axis at two points??

@bakedseal3369 7 жыл бұрын

cuz it is

@ahmedhasan3136 7 жыл бұрын

+BakedSeal ??!

@pgbrandon 7 жыл бұрын

f(x) is really the same thing as "y". What is the equation of the x-axis? y=0. Thus, setting y=0 gives you the zeroes or x-intercepts.

@KeyurKumbhare 7 жыл бұрын

notes2revise.blogspot.in/2017/03/algebra-khan-academy-notes-coming-soon.html

@Glamerth 12 жыл бұрын

119,820 Views......8 dislikes. HECK YES. =D

@mrhnm 14 жыл бұрын

When i factored it I got (2x+10)(x+5) can that work?

@zoomyracecar7849 4 жыл бұрын

When I multiplied it I got the starting equation so it should be acceptable

@nughson9868 4 жыл бұрын

This video was made 8 months after I was born...

@basalduat 13 жыл бұрын

x= -4 and x= -2 is correct but your drawing shows that x=2 and x =4 ???

@Mentalpathy 12 жыл бұрын

HOLY SHIT MY HOMEWORK QUESTION IS THE SAME THING HES DOING!!

@mikehawkins3766 3 жыл бұрын

Lol

@dansingcow5129 3 жыл бұрын

this was uploaded when i was 2 now im in gr 11 lmao

@tjnstoptens3690 3 жыл бұрын

Woah, i'm 12 now and i'm watching this like 8 years after

@nkolatsis 14 жыл бұрын

His mistake I would think. -6 +5 = -1 which +6 -5 does not equal.

@lukemcgregor6349 3 жыл бұрын

This was uploaded when i was not alive now im, a 7th grader lol

@thejrespotlight. 3 жыл бұрын

this was uploaded when I was -3

@Raf-qz7ih 2 жыл бұрын

i was -2

@DeptBookDave 13 жыл бұрын

I'm sure this is going to sound extremely foolish, but does anyone know any way to factor a quadratic with a 1 as the constant? Its status as the only single-factor number seems to mess up this process.

@lisinka3 15 жыл бұрын

EDIT: It's supposed to be f(x) = -9^2 + 441