Clear, articulate, precise. As a fellow Algebra Teacher I really enjoyed watching your instruction, I picked up a couple of things to use in my own class. Good Job
Hearing that teachers are out here engaging in their own development warms my heart. Thank you so much. I’m coming back to quadratics after ten years of failing it at school. My algebra teacher yelled at me for asking for real world examples so I could try learn quadratics application. Now it all is making sense!!!!
@@jessalisauskas7069 I don't really look back at any of my videos, so after recording them I hope that even years down the line it can still all make sense in such a way that people will engage in it and it is relevant to their coursework (especially when things like factoring and completing the square is involved). It seems this video is really doing it for people, and I'm just hoping that it's good enough!
Hey! You are amazing! I have been stuck on this subject since last week. You were the best teacher I found here; you speak slowly, and I can see how much you enjoy teaching. In just one hour, you helped me understand everything. Thank you very much for helping so many students!
What a great video! Thank you Professor Robinson. I especially like when you point out the fact that that parabolic curve does not mean that the object is moving from left to right as time progresses. As you point out, rather in refers to the change in height as time progresses. That is such a helpful hint, and I will use it in my session today with my students. Thank you again.
Thanks for the kudos, Dr. Mike! And please, I'm just Mr. Robinson haha! Although coincidentally enough, in my dream I brought my father into my classroom (who was a professor) and said to differentiate us, I would be Mr. and he would be Prof. Of course, I am leaving out the nugget that he been passed for over nine years, and that's why it's great to still dream about him as often as I do. Enjoy your session today!! :)
Thanks! I'm glad to hear this video has proven helpful for you. It seems this also pops up in people's searches so I hope it continues to help others as it did you. :)
Saturday I have the Sat test and thanks to you I finally understood how to complete the square and use in word problems the vertex form. Thank you so much for your help from Italy 🥇
So so so helpful! I sent this video around to everyone in my class. With finals coming up this vid was a life saver!!! You have earned yourself a new sub! :)
Hey awesome, thanks for the mention and I hope this helps you all understand what you already knew just a little bit better. Shoutout to Abby Hanifin! :) Curious, what class are you taking and are there possibly other videos on my channel that you may like me to direct you toward?
@@MrRobinsonsMathChannel Thx for the response! I'm in high school level Algebra 2 Hnrs. I am about to watch your logarithmic properties video. Do you have any vids on exponential growth & decay? We sped over it in my class.
@@abbyhanifin Hmm, word problems or which kind? I'll track down what I have because there is definitely something, but it's a bit sporadic. I will apologize since my channel is somewhat cluttered regarding content (these are made for my classes first and foremost without a thought of who else may be watching, haha), so whether you or I navigate through it may be a bit of a time suck. I'll do my best though!
@@abbyhanifin Okay Abby, I may have something up your alley but I want to confirm this is what you're looking for before I show you more on it, because the problems on the video will not really be next to each other. Look to this PDF for things regarding exponential functions: smallpdf.com/file#s=07b942f0-296d-4a51-96ba-39609f6f1b60 Page 1 has graphing basic exponential functions (no shifts, though I have videos with those if you need them), and pg. 2-3 has growth/decay model word problems. Are any of these of interest to you?
Thank you i finally understand what i didnt understand and what i need to do to figure out these word problems you made it so simple and easy to understand you are a life saver!!!!! Better than that 1 khan academy video you gave multiple examples and this is truly ging to help me ik it is!!! Thank you!!!!
Omg im so happy to have found you tomorrow I have my ib Math hl and sl placement test and we had the hint of it being quadratics and factorisation, this has definitely helped me with review as I can’t do word problems to save my life
This is fantastic! I don't know how RU-vid recommends certain videos/channels over others and how mine compares to others for information, but if this helps you the way that you need then I am forever honored to serve you!, Sven! :)
@@MrRobinsonsMathChannel Actually, we only have physics next school year (I'm an incoming g12). I was watching your videos as a review for college entrance exam.
Internet, my friend! I don't know if it was all one PDF, or if it was one that we assembled as a department, or if I said "I like these altogether" and I collected them all. Totally forgetful haha. Thanks a bunch!
Dammit Jason.... Thnx professor, doin precalc after 11 years away from education. I caught up pretty fast but these word problems have been the death of me... No pun intended
LOL RU-vid is a great platform for keeping these archived for the ages! I'm not teaching material this year that covers this, but I'm glad that in the future I can go straight back to this assignment myself and say "Here kids, watch this video if you need" and don't have to re-record it again. Glad that others stumble upon it along the way!
Thank you🩵 I gonna retest next week. I’m a foreigner and I not good in English, so I don’t understand my teacher😅.In class don’t have translate subtitles like RU-vid😂 anyway you teach very well.🤩
Thanks Professor Robinson for all clear explanation, but what I need I to request 2 questions (1) when did we use Discrimination =b^_2ab And how this formula drive from request full proof (2) how they drive from proof all in real life meaning if you don't mind. a) y =mx +b b) y= ax+b+c C) y = ax^+bx +c d) y =(x_h)^+k e) y =a(x_h)^+k f) y =a(x_s)(x_r) g) x= - b/2a Thanks
Unfortunately, I'm not sure how to answer the questions you're asking... mainly because I don't understand WHAT questions you're asking. Half of the formulas you wrote aren't even formulas themselves, or you're using incorrect symbols. If you can find a way to rephrase the questions, I'll make my best attempt to answer these questions. However, if they are not very answerable in text form, sadly I'm not sure how much I'll be able to help you regardless! I hope we can figure out what it is you're asking and get it taken care of. :)
only 6 minutes into the video and I am glad to have seen your account thanks man!!!! im in grade 10 and am a 60% student in math do you think I can still improve ?
Everyone can improve! The first valuable resource to overcome though, of course, is time. It takes a bunch of practice within, but yeah man it can happen! I'm glad you found this video helpful, and I hope I'll continue being able to help you in the future!!
On problem b I was stuck on the calculator part because at first you were talking about a discriminatory. I was just wondering that if we skipped the discriminatory part, if we could just the -b plus or minus the square root of -4 times a times b.
By "problem b," do you mean for #3? Yes, you can go straight to the quadratic formula. I do the discriminant first to expedite the process, because most of the work is done inside there (I explain that in other videos where my primary focus is the quadratic formula).
Mr. Robinson, a doorway has a parabolic arch. The base of the doorway is 3m wide. At a point 1.0m from one side of the doorway, it is 3m high. How do you determine an equation to represent this function?
Assuming we're placing one side of the doorway's base at (0, 0), that means we can place the other side at (3, 0). A third point we also will have is (1, 3). These are three (x, y) values that we can use to make an equation using the form y = ax^2 + bx + c. Your goal will be to find the a, b, and c that satisfy an equation in that form. Generally in the case of not knowing what your vertex is (even though we know the x value would be 1.5 since it's halfway between 0 and 3, we don't know what the y value will be), you would set up a system of three equations using your three (x, y) values in separate equations. In this case, using y = ax^2 + bx + c, your system would look like this: (0, 0) --> 0 = a(0)^2 + b(0) + c (3, 0) --> 0 = a(3)^2 + b(3) + c (1, 3) --> 3 = a(1)^2 + b(1) + c If I clean up each equation and put the y values on the right side, they'd look like this: c = 0 9a + 3b + c = 0 a + b + c = 3 Solving this system helps a lot because you get a true value for c as 0, meaning you can substitute that in the bottom two equations and get a system of two: 9a + 3b = 0 a + b = 3 You have a lot of options on what to do here, once of them being using the elimination method by rewriting an equation so that it cancels out one of your variables. If we divide the top equation by -3, we get: -3a - b = 0 a + b = 3 And adding these two equations, the b's eliminated and we get: -2a = 3 a = -3/2 = -1.5 Now we have the value for 'a'. Let's substitute that value into the equation a + b = 3 and solve for b: -1.5 + b = 3 b = 4.5 Okay, so a = -1.5, b = 4.5, and c = 0. So for our general quadratic equation y = ax^2 + bx + c, our final answer will be: y = -1.5x^2 + 4.5x I hope that helps! :)
At 23:17, shouldn't the acceptable answer only encompass 1 instead of both 1 and 7? Because it talks about after how many seconds will the rocket be, so after how many seconds after it took off from ground level? Thanks for your educational channel, it's been very helpful.
Hey, sorry that I completely missed your comment! Not sure if I understand your justification though. I keep re-reading it and I'm trying to figure out why it should only be 1 and not 7. I feel like for this problem type (and problems of the sort), they really do want you to find both answers. The only times they don't are when you have numbers outside of the domain, like getting negative time values that wouldn't apply to the model. Thanks for the props, though! I hope everything else was very helpful a couple of months ago! :D
Hi Mr Robinson, I'm two years late and it's kind of a dumb question but would that formula you used at the start for half a second be okay to use to find the TP of other quadratics? -(b)/ 2(-b). I'm just wondering because I was somehow never taught that there was another much shorter formula to find the TP
@@Elaine-kd6ri It's really cool once you find all the different ways that math connects to itself, or how you can use a proof to make one match with another. Glad you ran into the answer that you were looking for, Elaine! Oh, and don't think that you are late at all. This video is meant for you at YOUR convenience, and nobody else's. Twenty years from now, students who still won't even be alive through the next presidential term should be able to ask me a question about this video, and it would not be "too late" at all then, either! I'm glad this was able to help in some way. :)
@@MrRobinsonsMathChannel lol you're right, if I become in a math teacher in 20 years I'll be pointing them in your direction! thank you for the help :))
Hii, do u think u could do word problems that don't give you an equation but just height and width of something? I had a question about some bridge with certain measures and i didnt understand the question since i expected an ecuation :(
Perhaps! I'm not thinking of that type of question off the top of my head right now, though. If you recall what that question is later or have it on-hand, feel free to send it my way! :)
I’m sorry if this is a dumb question I’m just a little confused at 21:50 how are we getting t=7,1? wouldn’t -7 * 1 = -7? and -7 + 1 = -6 so how did we get it do add to -8? Thank you for your time
Hi Chloe. I think I see where I stirred you wrong. Out loud I indeed said "Negative 7 and positive 1," although I wrote -7 and -1. What I wrote was correct, what I said would be incorrect. Why did I say it? Not sure. Maybe when I said the 1 I was thinking about the answer that it would become. Just a brain fart, I suppose. I'm due for one or two of those. :)
Hi for question 2b. I was taught to always have the -16^2 to be kept as positive. So as the equation would be 112=-16t^2+128t i flipped it to 16t^2-128t+112. Then using the quadratic formula i got 1.7 and 6.2. Any idea why
Hi tripyyy, First of all, I think you were taught well to always keep it positive! You'll find that I do this on 3b (see 29:36). It benefits you in the long run, especially when it comes to work in the denominator. Heck, in any other problem where I do factoring (such as 2b), I also factor out the leading negative. As far as your solutions, I suppose what we would need to do is inspect your work. Even if you have the equation 16t^2 - 128t + 112 = 0 (and don't forget that zero, by the way), You should still ultimately get t = 1 and t = 7 by using the quadratic formula. Now, I'm a fan of dividing out common factors as I did (such as 16), but let's say you kept your numbers in there. So your formula would look like: t = [ -(-128) +/- sqrt( (-128)^2 - 4(16)(112) ) ] / [ 2(16) ] t = [ 128 +/- sqrt(16384 - 7168) ] / 32 t = [ 128 +/- sqrt(9216) ] / 32 t = [ 128 +/- 96 ] / 32 *t = 224/32 = 7* *t = 32/32 = 1* Check all of your values to see that you're substituting and simplifying properly. Feel free to check back with me on where you might have gone wrong, and I'll be happy to help you out! :)
@@MrRobinsonsMathChannel Thank you so much for helping out. I see my fault. I may or may not have made a mistake in the square of 128. Idk why lol. Thank you so much for the help
Glad to hear that even a few years later people like you can always continue to be helped! You're welcome, as this video isn't going down any time soon! :)
Hmm, do you mean like area/volume kinds of questions? A couple of my recent videos had some problems out of the textbook for sure. I'll have to search far and wide for them, but anything from Chapters 2-4 where they have word problems on Modeling Mathematics may have something you're looking for!
-b/2a is the way to find the x value of any vertex for a quadratic equation written in standard form. I don't suppose this comment section is the time to explain why this is the case, but if you know Calculus or look into the quadratic formula a bit you might see why this is true. Just keep in mind that this video is teaching word problems for quadratic equations, so I'm somewhat assuming we know how to use certain things on quadratic equations when you enter the video, such as finding the vertex. :) Thanks so much for asking!! Let me know if there is any other way I can help you!
Haha hardly a legend! Though coincidentally I was just telling my students "I hope my videos are still up after I die and people would comment later saying 'Mr. Robinson still be teaching us from beyond the grave!'" That's kind of a neat idea. I sure hope that's not for a long while though, heh.
Yes, of course! I try and avoid using completing the square unless I have an even linear coefficient (after factoring out anything in front of my quadratic term). See that you get the same answer by doing that if you try. :)
Where are you referring to this in particular? If you mean with regard to the functions, yes time is being squared, but it is a model representing HEIGHT as a function of time. So the question as to why "time is squared" is answered by the fact that the height of the object is dependent on it. Why does it depend on it? Gravity. Gravity is a force based upon acceleration, which means it expressed not how much an object changes position over time, but how much it changes velocity over time. Its units are not feet per second (ft/sec), but rather feet per second per second (ft/sec^2). This is what creates the parabolic arc of height (once again, due to gravity), and that occurs in the form of a quadratic model.
Fair enough. I can speed run through these questions as well (I can finish this whole assignment in under ten minutes), but the point of *my* videos personally are to teach the material itself to cater to the lowest common denominator (those learning it for the first time). I can excuse that by saying that one who is watching can still speed up the video, scrub through it, fast-forward it, or skip it entirely. There are other RU-vid videos out there that have expedited versions, and mine tend to not be those. I do have videos like that here and there though, and you'll find them; of course, whenever I do make these, I'll have several students that say I go too fast and don't explain a step that they wanted. In other words, I'm not doing the problems to teach the material (this is not what teachers SHOULD do with examples either). Instead, I am using the material to support what it is that I'm teaching. That way, when a student attacks a problem with some variations to it, they aren't completely dumbfounded because "it's not exactly like the last one but with different numbers." They have the luxury of opportunistically seeing more angles to it and they have a more general feel of what's happening. This is a conversational piece to give students an inner dialogue, particularly my students. I'm sure you know the Abraham Lincoln quote (which always changes the time around), saying something like: "If I had an hour to chop down a tree, I'd spend the first 45 minutes sharpening my axe." This video is mostly axe-sharpening, and then I chop away when I'm ready to go. By the way, I'm not saying you're wrong on how I approach these. I'm just saying that this is an intentional stylistic approach that I choose to use. I agree, we don't have 15 minutes to spend on a problem. Thankfully, these problems aren't your test. If you're interested in sending me a PDF of a word problem sheet that you have, I'll happily make a 15-20 minute version of a similar thing in contrast to this one though! :)
@@MrRobinsonsMathChannel Thank you so much for the offer and feedback, i understand what your trying to bring through these videos and its very much appreciated, My test is tomorrow therefore probably not enough time to make an explanation video
Hi there, it depends on how you're entering this as a whole. If you don't know the background behind factoring, quadratic formula, completing the square, vertexes, etc. then it can definitely be a daunting task. The purpose of this video was less on teaching how to do THOSE specific things (though I have videos on them if you want to hear more), but rather how to interpret the word problems as a whole. If you're still having trouble on the latter portion, I'm sorry that my video wasn't enough help on clarifying those portions.
Hmm, well I guess the bigger question is why would it be 6.75 feet? I showed where I calculated 2.25 feet from. I don't know how else I can explain "why it is what I calculated" outside of what I showed on the screen. I don't know where 6.75 feet comes from, or rather how a human jumps that high in the air to begin with haha. Did you do 9/4 + 9/2? I believe the 9/4 is negative when you multiply -16 by the squared value. Maybe that's where you got 6.75 from.
Hahaha never heard of him! Just looked him up, and I actually think one of my students from last year even looks much more like him, and I think he'd agree. But hey, if it's a compliment, then I'll take it! If not... well... I hope the video helped you! 😆
