Solving quadratic equations by square roots | Algebra II | Khan Academy

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  • Опубліковано 11 гру 2024

КОМЕНТАРІ • 302

  • @ashiyaprowell9563
    @ashiyaprowell9563 6 років тому +1053

    I’ve never been so confused in my life

    • @jaybabess_328
      @jaybabess_328 4 роки тому +11

      LMAOO same

    • @Yourfriendb3lla
      @Yourfriendb3lla 4 роки тому +79

      The second he changed out the 8 for 4 and 2, I was out of the game.

    • @janiyiaholliday
      @janiyiaholliday 4 роки тому +13

      I thought I was the only one

    • @1f2l
      @1f2l 4 роки тому +55

      math is the most cursed subject ever

    • @subestacionsantamaria4794
      @subestacionsantamaria4794 4 роки тому +17

      @@Yourfriendb3lla Hi Isabella, but 8 is the same number 4*2, you can try to see it this way, 8 inside is made up from (2+2+2+2) or you can also see it like 2 four times....or 4 times 2, (4*2)..

  • @Chaosflyex98
    @Chaosflyex98 12 років тому +34

    Hi Mr. Khan, thank you very much for doing this for the millions of people out there watching your videos. I'm taking Algebra I and this is helping a ton! I always move towards your videos when I am about to learn something or don't understand a new concept. God bless you, again I truly thank you very much. Keep up the amazing videos! ^_^

  • @betheboss5972
    @betheboss5972 8 років тому +267

    this is too confusing

  • @nfceastchampions2740
    @nfceastchampions2740 11 років тому +204

    What

    • @randallmokjialung3592
      @randallmokjialung3592 4 роки тому +11

      And so you've summed up my high school life

    • @preparator9925
      @preparator9925 4 роки тому +5

      @@randallmokjialung3592 and what will probably be my college life as well

  • @ducktape4221
    @ducktape4221 4 роки тому +86

    Thank you so much I was peeing during my math online class when the teacher discussed this ;-;

    • @ragedragon33
      @ragedragon33 4 роки тому +4

      lol idk why no one except me liked this

    • @vivixio2737
      @vivixio2737 3 роки тому +3

      @@ragedragon33 because this is the worst thing I've ever seen 💀

    • @woodstone7748
      @woodstone7748 Рік тому

      Heh

  • @12thmanrailfans26
    @12thmanrailfans26 5 років тому +262

    I learn nothing from my teacher. I learn faster from an 11 minute video than a 52 minute lesson

  • @-smp-scientificmethodpersp838
    @-smp-scientificmethodpersp838 5 років тому +51

    @5:13 for those of you who got lost, because he didn't explain what he was doing. He substituted one of his solutions for the x in the original solution, because he had solved for x. Since he solved for x, he can substitute what he solved for instead of using x. X=solution to be replaced with in substitution.
    The answer to the solution is to find what = 0. Well, 0=0 , so you have to prove that. In order to prove it, you need to get get rid of that unknown variable that needs to be solved for. In this case, it's x that is the unknown. So what do we do in algebra? Find X! After we know what x is, we can solve the original problem by replacing that x (unknown) with what we solved x to be (now known). Now we can solve the original problem. The original problem is 0=0 and you have to solve for that. The square root part in this video isn't to solve the problem (0=0). The whole square rooting part is to solve for x (X=?). Then use the answer for what x is to solve the original problem.
    If you still don't understand.... Yikes! Go watch some pre-algebra videos.

    • @alexswinton4978
      @alexswinton4978 3 роки тому +16

      My brain doesn’t like big paragraphs

    • @hannahahaha575
      @hannahahaha575 2 роки тому

      @@alexswinton4978 BAHAHA SAME

    • @Nataliah12
      @Nataliah12 Рік тому

      Thank you so much for your amazing effort of explaining ❤

  • @Bladesrcool
    @Bladesrcool 7 років тому +365

    Who needs a high school diploma?

    • @Alexis-kd9tm
      @Alexis-kd9tm 7 років тому +30

      people that want a job

    • @mattf.868
      @mattf.868 7 років тому +2

      Alexis Puente Well if algebra 1 or the regents in this case is holding you back for like 2 years I suppose you can go to trade school which I think doesn't need a high school diploma ( I dunno if that's true)

    • @neoz.9886
      @neoz.9886 6 років тому

      You need to pass the ALG EOC to get a high school diploma if I'm correct...

    • @gusskipner9809
      @gusskipner9809 5 років тому

      This is algebra 2

    • @xianflora8411
      @xianflora8411 4 роки тому

      Highschoolers

  • @sarahskup
    @sarahskup 12 років тому +7

    THIS HELPED SOOOO MUCH!!!!!! IM IN 7TH GRADE AND AM TAKING ALGEBRA 1, BUT I PROBABLY WOULD NOT HAVE PASSED PRE- ALGEBRA WITHOUT THIS GUY!!!!!!!! YOU RULE MR. KHAN

    • @ethanellis7864
      @ethanellis7864 2 роки тому +3

      your doing solving quadratic equations by taking roots in seventh grade? I'm genuinely curious because I'm in 10th lol

    • @ethanellis7864
      @ethanellis7864 2 роки тому +2

      wait a sec. i didnt even realize this was from nine years ago. holy cow

    • @sarahskup
      @sarahskup 2 роки тому

      @@ethanellis7864 haha seeing your reply was funny I’m 22 now and don’t even remember making this comment

    • @sarahskup
      @sarahskup 2 роки тому

      @@ethanellis7864 but yeah I was in an advanced math program so I was a few years ahead back then

    • @sarahskup
      @sarahskup 2 роки тому

      @@ethanellis7864 these videos really got me though honestly

  • @VanNintendo
    @VanNintendo 8 років тому +22

    You are awsome! You have helped me so much whenever I have a test!

  • @shaz85vw
    @shaz85vw 12 років тому +3

    Mr. Khan Your an absolute god send! Thanks so much
    Its been 10 yrs since i finished yr 12 and ive decided to go to university and do an associate degree of engineering and the text book we have to use is sooo mumbo jumbo and pretty relentless, but your explainations are brilliant. Thank you ever so much.
    Shannon

    • @wowo6460
      @wowo6460 4 роки тому +4

      shaz85vw did you graduate bro?

    • @i6zl135
      @i6zl135 4 роки тому

      its been almost 10 years, are you good bro?

    • @NathanRio79
      @NathanRio79 3 роки тому +1

      I think "shaz85vw"is still an active (or at least rarely active) UA-cam Account.
      This account has a "Favorites" Created Playlist and the latest video in the playlist is from October 2020.

  • @teachmechannel6828
    @teachmechannel6828 6 років тому +13

    Thank you so much for this great lesson. I was searching so hard for this kind of extracting square root, then I found this video. THANK YOU SO MUCH😇

  • @nightowl538
    @nightowl538 3 роки тому +2

    It's been 11 yrs but generations still use it till now

  • @cyodissnips8086
    @cyodissnips8086 4 роки тому +46

    Me at the end of the video not understanding any of it: wut
    Him: Well, that was a good warm up

  • @airasagmon262
    @airasagmon262 2 роки тому +1

    im from philippines Thank u sm
    I might Ace the math exam tommorow thanks to u😂

  • @debo3822
    @debo3822 5 років тому +4

    Imagine this, but explained MORE complicated than it should be. Thats my teacher y'all

  • @heyitsjaee222
    @heyitsjaee222 7 років тому +26

    my brain has so much smoke coming out of it 😐

  • @OffTheBeatenPath_
    @OffTheBeatenPath_ 9 років тому +97

    Really poor example to use the square root method.

    • @stevenf5902
      @stevenf5902 6 років тому +1

      OffTheBeatenPath Why?

    • @Roblafo
      @Roblafo 5 років тому +10

      @@stevenf5902 because 8 doesn't square root into just a number so he had to write it weird which is confusing for most people trying to learn this.

    • @Reagandover1
      @Reagandover1 5 років тому +2

      Yeah I’m trying to learn the actual method but he’s doing a bunch of different ones he does factoring aaaa

    • @PsychoEye
      @PsychoEye 5 років тому +2

      @@Roblafo that was right since it wasnt a perfect square

    • @jewellpetalcorin3093
      @jewellpetalcorin3093 4 роки тому +1

      2x²=7 is much better example

  • @dollyspine
    @dollyspine 2 роки тому +2

    helping me pass my final exam tomorrow, THANK YOU

  • @repentnowjesusiscomingsoon7356
    @repentnowjesusiscomingsoon7356 2 роки тому +4

    Romans 1:16 For I am not ashamed of the Gospel for it is the power of God unto salvation to every one that believes.

  • @jlklai98
    @jlklai98 12 років тому +1

    If only my teacher could be as good and clear in Algebra as Mr. Kahn. Thanks for the little clarification!!!

  • @janiyabeene6200
    @janiyabeene6200 2 роки тому +3

    Thank you so much. I have a quiz tmr and I was bound to fail. Now I feel much more confident!

  • @rochellezhaynesabac5243
    @rochellezhaynesabac5243 7 років тому +82

    i didnt understand a single thing

    • @kaygee8260
      @kaygee8260 7 років тому +8

      Rochelle Zhayne Sabac You need to know some other concepts about quadratics to fully understand this

    • @kevinalex-pq2sh
      @kevinalex-pq2sh 4 роки тому

      me neither lol

  • @tanyanathani
    @tanyanathani Рік тому

    I have a quiz tomorrow this really helped me, I wish my teacher thought like this otherwise I wouldn’t have to self learn every time I go home

  • @pmpdaddy
    @pmpdaddy 2 роки тому

    off the addy rn feeling good preciate it khan

  • @anshugupta000
    @anshugupta000 6 років тому +13

    Sir please make a video how to factroise. √3x² + 10x - 8√3 = 0

  • @saxofan9972
    @saxofan9972 6 років тому +1

    Thank you. This really help me a lot

  • @despiadado3447
    @despiadado3447 4 роки тому +1

    thank you so much i have a algebra 2 mid test due in 2 hours

  • @ashtonhartis7480
    @ashtonhartis7480 2 роки тому

    thank you this didn't help as much as I wanted it to. but it did help a lil bit thank you

  • @Tenshar1
    @Tenshar1 13 років тому

    Thank you so much, because it was just not clicking with me at all....God bless you!!!!

  • @diegocordero676
    @diegocordero676 6 років тому +1

    You're doing all the easy ones

  • @BuwiBeastsGaming-nv8ey
    @BuwiBeastsGaming-nv8ey 3 місяці тому

    14 years ago and still so useful

  •  6 років тому +4

    over doing it can be confusing ...

  • @Mark-jh4mt
    @Mark-jh4mt 7 років тому +3

    Thanks! Helped me alot, the last two equations are not taught to my class yet so i might get a head start from this! Thanks again!

  • @vchivaaree
    @vchivaaree 8 років тому +45

    waaaaa. I don't understand anything

    • @カツハ-z7z
      @カツハ-z7z 8 років тому +3

      Just use the x2 for square root and divide 8 into 4x2

  • @bananiaman3162
    @bananiaman3162 10 років тому +3

    Thanks a lot! This really saved my a$$ :)

  • @MasoomaKhan-i8t
    @MasoomaKhan-i8t 6 місяців тому

    This was so easy and clear to understand idk why people seem confused

  • @anydragon4811
    @anydragon4811 4 роки тому

    i had one question and you answered it in the first 2 minutes

  • @cherryson4625
    @cherryson4625 4 роки тому

    Tmro is my maths test thanks soo much

  • @timbarrett8803
    @timbarrett8803 11 років тому +1

    I just bombed a test on this, and now it makes so much sense! Thanks!

  • @Sautiyadhahabutv
    @Sautiyadhahabutv 4 роки тому +1

    Good

  • @yuinurahilyon5711
    @yuinurahilyon5711 5 років тому +7

    Bizarre equation.
    Me: glad you know.

  • @scorpionkiller8408
    @scorpionkiller8408 2 роки тому +1

    thank you so much i just got my test result in math my score is 39/50 yay

  • @カツハ-z7z
    @カツハ-z7z 8 років тому +12

    FINALLY I GOT IT!

  • @madmaxout0
    @madmaxout0 8 років тому +8

    i was taught differently

  • @memuggleman
    @memuggleman 10 років тому +6

    What do you do with a problem like:
    2x^2-12x+18=32?
    I don't know how to do the 2x^2 part

    • @hairlessopossum4042
      @hairlessopossum4042 7 років тому

      memuggleman lmao sorry a little late bate take the squre root of it making it have not exponent. If negative use the original answer if it were positive and add i

    • @justintimeboi31
      @justintimeboi31 6 років тому +8

      Y'all are answering his question 3 years late.

  • @keilynrobison8002
    @keilynrobison8002 6 років тому

    thanks your really helpful

  • @maximocaceres4685
    @maximocaceres4685 2 роки тому

    Love your videos

  • @blessings1063
    @blessings1063 3 роки тому +3

    10 minutes of nothing overcomplicating simple things and not explaining the confusing stuff

  • @maxferia2714
    @maxferia2714 11 років тому

    Woot I finally get this

  • @realyours643
    @realyours643 4 роки тому

    thankyou so much

  • @subhashpoonia8193
    @subhashpoonia8193 3 роки тому +1

    I am from INDIA🇮🇳. And watching for 10th class exam📄. But shocked to see the time of uploading the video. 11 years ago
    👇. 👇🏼

  • @patrciaclemons8183
    @patrciaclemons8183 Рік тому +1

    I learn this in 1 week at college, get tested, and never look at it again. What is education

  • @anasaleem1
    @anasaleem1 6 років тому

    Khan acadmy always blown up my mind give a like if u agree

  • @cadepriola5075
    @cadepriola5075 2 роки тому

    Sounds like Andre from The League✊

  • @gavinbriggs2020
    @gavinbriggs2020 5 років тому +1

    Thank you! Wish my teacher could teach like you...

  • @purr2564
    @purr2564 3 роки тому

    TY OMGG

  • @LexiiCharms
    @LexiiCharms 12 років тому

    I want you to know that you are saving my life. Thank you so much.

  • @Frindow
    @Frindow Місяць тому +1

    this is so easy how are y’all not understanding 😭

  • @lilivrse5794
    @lilivrse5794 5 років тому +2

    This is exactly how our teacher discussed it

  • @tigrrlily2569
    @tigrrlily2569 4 роки тому +5

    I have a test tmr and am trying to drill this information into my head but I'm honestly so confused help...

    • @hudsongoff8922
      @hudsongoff8922 4 роки тому

      Tigrrlily25 how’d it go?

    • @tigrrlily2569
      @tigrrlily2569 4 роки тому +2

      @@hudsongoff8922 Oh I actually got 100%! It wasn't as hard as I'd expected it was going to be.

  • @kadapi1972
    @kadapi1972 11 років тому

    as x-8 = 0 or x-2=0, in solving, the answers turn out to be positive 8 and 2

  • @johnpuri4317
    @johnpuri4317 8 років тому +1

    How to solve with 1/3 power? e.g (1+x)^(1/3) + (1-x)^(1/3) = 2^(2/3)

    • @tobisteindl951
      @tobisteindl951 8 років тому +2

      1/3 power is like the third root of something. So you have to find 3 equal parts that multiply up to that number. For example 8^1/3 is 2 because 2^3 is 8

  • @MelissaMachine5000
    @MelissaMachine5000 11 років тому +7

    Who else is here for Algebra HW

  • @14hazel
    @14hazel 6 років тому +6

    Why do they even teach this in school. We arent even gonna be using these formulas in our everyday life -_-

  • @brooklynnmetz8767
    @brooklynnmetz8767 8 років тому +1

    I really must figure out what program he runs for the "chalk board". It would come very handy at one point or another

  • @TheJunkieBox
    @TheJunkieBox 14 років тому +3

    Haha, I did all this Algebra I stuff about a month ago. This would have been really nice then. >xP

    • @TheKarakRecords
      @TheKarakRecords 7 років тому

      good meme

    • @gamechip06
      @gamechip06 3 роки тому

      This dude is 11 years older than when he made this comment

  • @OMGitsANJA
    @OMGitsANJA 12 років тому

    my thoughts exactly

  • @cheery_cherry6756
    @cheery_cherry6756 3 роки тому

    9:00 can you use the quadratic formula to solve these still?

  • @jennifercano1541
    @jennifercano1541 11 років тому

    Awesome

  • @shrushtivipinmota.1977
    @shrushtivipinmota.1977 6 років тому

    finally I got it

  • @ashitbhagat2510
    @ashitbhagat2510 7 років тому

    great

  • @YasiaAliyah
    @YasiaAliyah 9 років тому +2

    Im confused on the last equation. Why would we subtract 1? Is it because of x squared?

  • @ItsHayden
    @ItsHayden 7 років тому +14

    idk why but to me this guy sorta sounds like Yandere Dev

  • @mouthfulasouth
    @mouthfulasouth Рік тому

    I need the last step!!! Solving the square root part because that's not explained in any other video 😫

  • @munchlady1670
    @munchlady1670 8 років тому +1

    what if you have two different letters all together like r^2-8t+24=0

  • @krishis2286
    @krishis2286 5 років тому +2

    I lost it at 4:53 but whatever

    • @16letter68
      @16letter68 4 роки тому

      they subtituted the value of x i think

  • @celiodochka8027
    @celiodochka8027 Рік тому +2

    my test is in 20 minutes and i’m confused, hope this helps

  • @adijoshi4751
    @adijoshi4751 Рік тому

    it's wild to think this videos 11 years old

  • @erikawhite5582
    @erikawhite5582 8 років тому +1

    what if the equation is -3(x^2-1)=121

  • @justsomeguy1474
    @justsomeguy1474 2 роки тому

    This isn't even confusing lol I just learned it pretty ez then forgot it cause we went on break now I got it on a test

  • @kylamartinez4100
    @kylamartinez4100 7 років тому +2

    can someone teach me how to solve 3x^2+1=28

  • @1f2l
    @1f2l 4 роки тому +1

    what app do you use to write?

  • @jyugonanbaka4344
    @jyugonanbaka4344 5 років тому

    So what will you do if you have the ax2 + bx + c=0 form rather than ax2 + c form?

  • @FunWithAaron
    @FunWithAaron 12 років тому

    Crystal clear now! I feel like watching all of your videos. It's like you go from being dumb, to being a genius after watching just one! Lol

  • @motobmurray
    @motobmurray 12 років тому

    @SpartanKingOnverser Hey it's Ralph

  • @marshalltoby6994
    @marshalltoby6994 3 роки тому +2

    i have a test in less than thirty minutes and im extremely sure i wont pass the test nor this school year

    • @Vi.0.9
      @Vi.0.9 3 роки тому +1

      so did you pass it or not

    • @marshalltoby6994
      @marshalltoby6994 3 роки тому +1

      @@Vi.0.9 i did but i cheated so HAHA-

    • @jonasward5977
      @jonasward5977 3 роки тому +6

      @@marshalltoby6994 Congratulations, on passing, while some may say cheating is wrong, I would argue forcing kids to learn this crap is even more wrong. I hate math so much.

    • @marshalltoby6994
      @marshalltoby6994 3 роки тому

      @@jonasward5977 thank you! i hope math this year and in the future is treating you well. im currently procrastinating on math by checking all my notifs 😔

    • @woodstone7748
      @woodstone7748 Рік тому

      HAHAHA

  • @prophecy4270
    @prophecy4270 2 роки тому +2

    I’m quitting school

  • @MexicanCat999
    @MexicanCat999 12 років тому +2

    why can't you replace my Algebra 2 teacher?!

  • @maggied.metalhead7804
    @maggied.metalhead7804 4 роки тому +3

    Man I hate math

  • @asame186
    @asame186 4 роки тому

    4:09 sir IM PRETTY SURE THATS -4

  • @black3ru
    @black3ru 3 роки тому +1

    math kills my braincells haha

  • @harveychan1024
    @harveychan1024 4 роки тому

    How to solve 2(×-2)^2=12

  • @luvjake3670
    @luvjake3670 3 роки тому +1

    and suddenly I can’t understand english anymore

  • @AKJaglan
    @AKJaglan 4 роки тому

    how can we find root of a^2=110+√a

  • @motobmurray
    @motobmurray 12 років тому

    If only if only there was a way. For him to teach his subscribers L.A. If only if only he could expand his horizon. Beyond solving quadratic equations. If only if only he could hear me fart. Wanting him to teach Language Arts..

  • @snitchinkitty2421
    @snitchinkitty2421 7 років тому

    1:50 are u not supposed to put an i on the negative 8?

    • @andrew1925
      @andrew1925 7 років тому

      KnittingGoAt ' only if the -8 is inside the square root. So if u had a positive 8 then moved it over it would be -8. The + or - is just saying there are 2 solutions where u either had or subtract.

  • @berrell51
    @berrell51 11 років тому

    Watched this for Mid Semester Test...

  • @users4007
    @users4007 2 роки тому

    1 hour class is a waste of time when i could simply watch a 10 minute video and understand subject better

  • @jxckii.w
    @jxckii.w 2 роки тому +1

    i got a test today on this stuff :) imma fail