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

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  • Опубліковано 11 лип 2011
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    Application Problem with Quadratic Formula
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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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КОМЕНТАРІ • 143

  • @EmmysCoolVids123
    @EmmysCoolVids123 7 років тому +291

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

  • @bawbee2389
    @bawbee2389 4 роки тому +123

    Me in quarantine: laughs in Photomath

    • @tylersakul2633
      @tylersakul2633 4 роки тому +5

      ROZELLE photomath works for this?

    • @gallaghergirl427
      @gallaghergirl427 4 роки тому +6

      @@tylersakul2633 if you take a picture of the formula then yeah...

    • @glasslicker2829
      @glasslicker2829 3 роки тому +2

      Casuals

    • @anubhavbehera3721
      @anubhavbehera3721 3 роки тому +2

      Lmao yes

    • @yaboiyammsta2721
      @yaboiyammsta2721 Рік тому

      HAHAHAHAAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHHAHAHAHAHHAHAHHAHAHAHHAHAHAHAHAHHAHAHAHAHAHAHAHAHAHHAHAHAHAHHAHAHAHAHAHAHAHAHHAHHAHAHAHHAHAHAHHAHAHAHHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAH

  • @davidchillton1744
    @davidchillton1744 7 років тому +143

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

    • @tylerkihut8328
      @tylerkihut8328 4 роки тому +9

      Baseball

    • @vibewithfav
      @vibewithfav 4 роки тому +1

      David Chillton frr

    • @time_lightsout_1186
      @time_lightsout_1186 3 роки тому +9

      Business applications it's the same concept from same formula.

    • @kkboligor7409
      @kkboligor7409 3 роки тому +5

      i kinda believe we should focus more on this than others because like its basic physics but this isn't explained as well and as much

    • @malachinicks4257
      @malachinicks4257 3 роки тому +9

      Shut up and learn

  • @PatrickCraig-lh5is
    @PatrickCraig-lh5is 8 місяців тому +4

    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.

  • @likwah
    @likwah 4 роки тому +24

    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

  • @godlybunniarts8549
    @godlybunniarts8549 4 роки тому +9

    stop reading comments and study

  • @sagestopmotions5151
    @sagestopmotions5151 2 роки тому +11

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

  • @clashofclansdogdowlers4111
    @clashofclansdogdowlers4111 6 років тому +17

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

  • @bobboberts3651
    @bobboberts3651 3 роки тому +7

    khan academy pulling through rn 🙏

  • @ry6234
    @ry6234 2 роки тому +6

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

  • @wyatthollingshead1216
    @wyatthollingshead1216 8 років тому +19

    SLOW DOWN

  • @khalidnassar2172
    @khalidnassar2172 9 років тому +11

    You saved ma life

  • @julietacortese8373
    @julietacortese8373 2 роки тому +4

    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

  • @ecaj400
    @ecaj400 3 роки тому +6

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

  • @moki2003
    @moki2003 6 років тому +4

    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)

  • @maracas3894
    @maracas3894 3 роки тому +2

    Where did the 16t² come from?

    • @sohambagad8202
      @sohambagad8202 Рік тому

      It was in the equation given in the problem

  • @chocolateshmurda5818
    @chocolateshmurda5818 7 років тому +4

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

    • @chocolateshmurda5818
      @chocolateshmurda5818 7 років тому +3

      and for all y'all who saying "slow down" it's called pause the video and work your problem slowly, genius

    • @larryreddell2974
      @larryreddell2974 2 роки тому

      Simply "I hate algebra" would have worked better.

  • @BobBob-uv9fq
    @BobBob-uv9fq 2 роки тому +4

    Really useful ,more example like this would be great

  • @MidnaTriforce
    @MidnaTriforce 11 років тому +11

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

    • @breewelchh
      @breewelchh 3 роки тому +1

      the square root of -1 is i

  • @javierrod1987
    @javierrod1987 4 роки тому +1

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

  • @BobBob-uv9fq
    @BobBob-uv9fq 2 роки тому +1

    It really is very easy when one knows the system

  • @blessysagmit8093
    @blessysagmit8093 4 роки тому +4

    Me rn;
    How you like that?
    Guys! Can you teach me how to solve this lesson? Huhu

  • @TheJatt50b
    @TheJatt50b 9 років тому +7

    Khan academy i love you

  • @kooroshtg4419
    @kooroshtg4419 7 років тому +3

    You didn't have to use the quadratic formula, as -5 and 5 multiply into 25 and 4 and 2 multiply into 8 and the sum of their product gives you -10, so you might as well write 0= (4x-5)(2x+5) and solve for the x values by setting them to 0 individually.

    • @haani4745
      @haani4745 4 роки тому

      Can u please explain me why did he divide the equation by 2 at first?

    • @kowboi6451
      @kowboi6451 11 місяців тому

      3 years late but he did that just to simplify the function! It's not necessary, but it makes your values easier to work with
      @@haani4745

  • @larryreddell2974
    @larryreddell2974 2 роки тому +1

    The equation is easy to follow, However - It would be nice to know where the -16t squared comes from. -16xsquared must be a standard but this problem doesn't explain where one can find such a (seemingly) constant value to plug into the equation. Is there a list or table somewhere with such information?

  • @soonerfan0161
    @soonerfan0161 3 роки тому +1

    Where does the -16 come from?

  • @dirkfield
    @dirkfield 12 років тому +2

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

  • @clashofclansdogdowlers4111
    @clashofclansdogdowlers4111 6 років тому

    thanks for the help

  • @clythx
    @clythx 3 роки тому +1

    I am wondering of the first term's origin, where does -16t^2 comes from?

  • @alfredoavila3706
    @alfredoavila3706 5 років тому

    is the way that you did it longer?
    because i automatically just applied the quadratic formula and still got the correct answer but quicker

  • @tylercheek3652
    @tylercheek3652 5 років тому +4

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

    • @haani4745
      @haani4745 4 роки тому

      Yeah even I don't get that

    • @cameron6031
      @cameron6031 4 роки тому +2

      He factored the equation

  • @hddevani
    @hddevani 8 років тому +3

    but ; maths does not give waste answer...; then what does that (-5/4) mean???

    • @Eggsec
      @Eggsec 8 років тому +1

      means the ball started has dark matter, neg velocity

    • @Eggsec
      @Eggsec 8 років тому +1

      then; kinematics must be apply!

    • @tylercheek3652
      @tylercheek3652 5 років тому

      It means you can't simplify any more

  • @carrevenger31
    @carrevenger31 5 місяців тому

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

  • @nolapreema4682
    @nolapreema4682 3 роки тому +1

    I have one question, Where did you get 16t?

    • @time_lightsout_1186
      @time_lightsout_1186 3 роки тому

      Gravity is 32ft per sec ² and the equation you originate the formula from is -1/2 of that so -16x²

    • @mackenziecolebrook7223
      @mackenziecolebrook7223 3 роки тому

      Does that apply to all equations?

  • @MultiPG23
    @MultiPG23 11 років тому +1

    I have a problem solving this word problem: A square lawn is surrounded by a concrete walkway that is 2.0 m wide. If the area of the walkway equals the area of the lawn, what are the dimensions of the lawn? express the dimensions to the nearest tenth of a meter.
    I have tried many times modelling the problem but always get stuck, can u please help. Thanks

  • @autumnsimlerthepinkninja251
    @autumnsimlerthepinkninja251 6 років тому

    this is helpful

  • @fkf055
    @fkf055 9 років тому

    Bruhhhhhh your amazing

  • @notonlyy0urs518
    @notonlyy0urs518 3 роки тому

    Why would it had to divide them by negative 2? Why??

  • @progone149
    @progone149 7 років тому +1

    Where did you get the 16t2?

  • @theophonchana5025
    @theophonchana5025 2 роки тому

    b^(2) - 4ac = 900

  • @CloudLucisCaelumCXV
    @CloudLucisCaelumCXV 4 роки тому +1

    Whawha....?

  • @sparkles163
    @sparkles163 7 років тому +2

    This didn't have me cause ya writing on a black board and I can't see it good

  • @engr.tonystark3504
    @engr.tonystark3504 Рік тому

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

  • @punyan775
    @punyan775 5 років тому +2

    Can you solve this without simplifying? I got 60/-32 which = -1.875

  • @c.wr.w9761
    @c.wr.w9761 7 років тому

    What about solving for height

    • @chrystalreed456
      @chrystalreed456 6 років тому

      C.W R.W height becomes the h in y=a(x-h)+k which is also called the vertex form

    • @chrystalreed456
      @chrystalreed456 6 років тому

      The maximum height rather

  • @jacob3800
    @jacob3800 11 років тому

    He's never claimed to be Muslim. Just because his name looks Bengali doesn't mean he's Muslim.

  • @alinaparker1937
    @alinaparker1937 3 роки тому

    where did the negative 16 come from

  • @ismailbranko1729
    @ismailbranko1729 5 місяців тому

    I got test tommow, but I don't get it.

  • @Eggsec
    @Eggsec 8 років тому

    the answer has to be neg, you could already tell by the beginning of the prob, "A ball is shot into the air" by that the ball already the ball has some sort of the velocity when it reaches the edge of the building. now keep on mind they want to know how long it takes to hit the ground. well thats where the neg answer comes from bc it already trav at a x speed.
    to find a pos answer we first have to know at force/speed it was thrown up in the air. now the force its tricky bc depending on the force the ball could of travel upwards reaching x altitude, picked up x speed downward, and this is not taking in consideration the weight of the ball and so on blah blah.

    • @Eggsec
      @Eggsec 8 років тому

      it said, it initial velocity is 20ft per sec, this is the velocity when it met at the edge of the building. the problem should of had started like, a ball is drop from the edge of the building....

    • @jakedickens4771
      @jakedickens4771 7 років тому

      Let me know when you can go back in time, and then ill believe you.

    • @ravegames1003
      @ravegames1003 4 роки тому

      this one dude with that huuuge explanation

  • @eliehmaeriejulao1830
    @eliehmaeriejulao1830 5 років тому +1

    San nyu po nakuha ang 16?

  • @JD-ez8fg
    @JD-ez8fg 6 років тому

    Why u use the square root

  • @noelletreloar6064
    @noelletreloar6064 2 роки тому

    i love you

  • @catherynespinosa444
    @catherynespinosa444 3 роки тому

    Where he get -16 from

  • @chadyes347
    @chadyes347 4 роки тому

    Why divided by -2? 1:30

    • @moodafan123
      @moodafan123 4 роки тому

      To simplify the equation, doing that would make it easier to solve. If you don't simplify you'll get the same answer but it would just be harder. He did -2 because they're divisible by that number.

    • @notonlyy0urs518
      @notonlyy0urs518 3 роки тому

      @@moodafan123 but why negative 2 ? neither positive 2?

  • @humanvoice369
    @humanvoice369 2 роки тому +1

    why would someone want to calculate something like this? why are these problems always like you are solving for the heck of it. how boring.

  • @madelein3167
    @madelein3167 6 років тому

    wait, i don't get why you divided it all by two?

    • @pump.queenz
      @pump.queenz 4 роки тому

      You can just factor out a -1 to make it positive he did the most

  • @eldonallen497
    @eldonallen497 3 роки тому

    Sir, can I use the bathroom?

  • @julietgalido9979
    @julietgalido9979 3 роки тому

    Can someone tell me where -16 came from? :

  • @autumnsimlerthepinkninja251
    @autumnsimlerthepinkninja251 6 років тому

    *coughs* the heck

  • @muhammadbilalbilal170
    @muhammadbilalbilal170 2 роки тому

    -16 t kha sy a gya smJ nhi aya😮

  • @sachin1q
    @sachin1q 13 років тому +3

    FUCK YEA!!
    FIRST COMMENT!!!

  • @pump.queenz
    @pump.queenz 4 роки тому

    Bruh you don’t have to simplify

  • @almarubii
    @almarubii Рік тому +1

    im failing bruh

  • @Norman_Lazarevich
    @Norman_Lazarevich 5 років тому

    Someone help me...the question I'm trying to answer just give me the equation and no other.Any Idea?

  • @devil_editz128
    @devil_editz128 2 роки тому +1

    Bhai ye banda dusro ka vedio copy paste karta hai

  • @user-zo3ph3xs1u
    @user-zo3ph3xs1u 3 місяці тому

    Who is here 2024 😂

  • @Aesieda
    @Aesieda 11 років тому

    Good job my Muslim brother!
    You should do some Islamic lessons and people will actually listen to you because of your wide knowledge!

  • @susantparida8369
    @susantparida8369 4 роки тому

    You can just divide 50 by 20. Duh.