I'll be honest, I don't pay attention in class because I know I'll just come home and watch The Academy's video. The bonus factor is that I will understand in under 15 minutes what my teacher struggles to explain in 50 minutes.
I wish they'd go through equations that didn't work so well. ike equations where you have to do a little more and it doesn't all just seamlessly fit together
I want to cry, ive been studying this for hours and just couldnt get it (have a math test tomorrow). This video made me understand it all THANK YOU SO FUCKING MUCH
I get it on here but look at my homework and go what is this. My homework is out of the prentice hall algebra 2 book and you can learn one thing sitting in a class where the problems are simple but get the homework and it’s like I don’t understand it.
+Anonymous User Using the "quadratic formula" you can determin what X is equal to. So if you get a complicated question where your final quadratic cannot be used by factoring, you use the quadratic formula.
Is the... method of transforming rational algebraic equatiion to quadratic equation present .?? Right Thanks .....a lot... i owe you ..my presentatio and assignment ia pres...
at 4:25 I dont understand how you take x^2 + 2x -8 and factor it down to x+4 times x-2. I see were x+4 is because the power of two but i cant figure out how you get the x-2
Here's the explanation even though it's super late hahaha He factored the denominator x^2+(2)x+[8] ____+____=(2) ____•____=[8] ^ ^ 4 -2 So the factored form of x^2+2x-8 is (x+4)(x-2)
I learned that shit already in advance math but we never simplfied the square root... We left it as it was bc we werent allowed to use decimals unless it was a perfect square and 113 isnt a perfect square...
Haha he turned the equation into a quadratic formula. It’s how you can solve quadratics and you can do it when you have an equation where the first term has an x and is squared, and second term with an x (not squared) and a regular number. When there are usually three terms like that, you can plug in the values (not including the x’s) into the quadratic formula to solve the quadratic.
Hi, I have a question I'm struggle with for hours now. Why do we not multiply the denominator by the Least Common Factor too if we're solving the equation? But if we're simplifying an expression, dont we have to multiply both nominator and denominator by the LCF too?
Thanks, this video was very helpful for me. Tomorrow I'll be taking my math exams and rational equations were one of them.. Thanks a lot Khan Academy!!!
But he's not explaining the quadratic formula in this video, therefore, he would just get through it fast. The explanation for solving rational equation was pretty detailed though.
You can solve it in your head, but if you don't have a calculator you can leave the square root without solving it. You could also simplify the radical expression, unless its a perfect square root. Its weird that you're not allowed to use a calculator though
He just simplified both sides of the equation. He had: 5/35 = 2/14. 5 divided by 35 = 1/7. 2 divided by 14 = 1/7. Since 1/7=1/7, that means that the value of "x" which he put in is the correct one and is a solution.
My teacher does a horrible job explaining things, plus the fact that she just shows us what to do instead of how and why you do it, and on top of THAT it's hard for me to understand math quickly. This really helped. A 42 minute ill explained lesson compressed into a 13 minute well explained lesson
I'm confused as to how you were able to rewrite x^2+2x-8 into x+4*x-2. I know it is possible, but I don't know how you did it. If someone could explain this, that would be great (: @4:26
Hey, I know am 3 years late but there may be others with the same question as you so here I'll simplify it step by step. Step 1: AC Method The quadratic x^2+2x-8 is in the form ax^2+bx+c. This will work for any trinomial. It's called the AC Method because we multiply A and C, which in this case is 1 (because the coefficient of x^2 is 1) and -8 and we get -8. Step 2: Factoring Now that we have the number -8, we have to find a pair of numbers that when multiplied will equal C (-8) and when added will equal B (2). You can go ahead and list the factors, like 1 and -8 is a pair, or -4 and 2. Once you get the hang of it, you can quickly factor in your head. He saw that 4 and -2 multiply to get -8 and add to get 2, which is why he ended up with turning that into (x+4)(x-2). Hope this helps :)
@@jah-4 Haha, well thanks anyways! I'm sure it helped others. 3 years later, I can look at the equation and figure it out now, so I guess I am testament to the success of the schooling system.
I know this comment will go unseen here, but I'd feel guilty if I didn't thank Khan Academy for the full lesson they just taught me in less than a quarter of what my teacher would spend on the same topic. Thank you!
I don't know how fast you could respond to this question but in my college algebra 1 class I'm struggling to understand this equation with rational equations. It's x^2 - 10x + 25/ 3x-5
I've been struggling with this for so many hours, I have a quiz I need to asnwer due today and the way our teacher taught us in our online class, I didn't really understand. Thanks for the vid!!!
For the future people cramming their Algebra test (like me hehe) and scrolled down the comments section to ask where the hell the square root came from, it's because he used the quadratic formula to factor the equation. And you SHOULD know what the quadratic formula is, since you should've learned that from solving quadratic equations.
I'll be honest, I don't pay attention in class because I know I'll just come home and watch The Academy's video. The bonus factor is that I will understand in under 15 minutes what my teacher struggles to explain in 50 minutes.
So true
hahaha me 24/7
mine is different i pay attention to class and dont understand shit then come here but still 50/50 im at grade 11 by the way
I'm at Grade9 and damn it's so hard.
8th grader here. Can't understand a thing
Why is math so god damn difficult
retweet
Because you don't study?
It’s made to be confusing .....
@@diegocordero676 its the skill, you're just being dry
@@aiexzs simp
Lost me at the end
All this work would make you think you solve something super complex.
Nope. Just a line on a graph.
I hate my life.
I wish they'd go through equations that didn't work so well. ike equations where you have to do a little more and it doesn't all just seamlessly fit together
Exactly
Math is the devil's language.
Addie Seidel Don’t put that evil on him. 😂, he’s about having fun.
@@el290 😂 have you seen the tv show Lucifer yet?
Faaaaaaacts!
I want to cry, ive been studying this for hours and just couldnt get it (have a math test tomorrow). This video made me understand it all THANK YOU SO FUCKING MUCH
You're welcome.
Please don't swear in this minecraft christian server
How are you now?
Remember when a math problem could be written in 5 seconds not 12 minutes??
This 12 minute video has me understanding this unit more than my teacher trying to teach me for 55 minutes...
+Bobby V I know right. Me too.
Yeah same with me too. Wish all our teachers we're like this video, short and simple
Exactly
I dont comprehend well so i understand but my class period is 90 minutes so i would know you pain. Im not that good in Algebra 2
Sometimes I wish that I have the same mind as the one speaking in terms of mathematics.
Sal, first of his name.
Love your headshot
Same.
I get it on here but look at my homework and go what is this. My homework is out of the prentice hall algebra 2 book and you can learn one thing sitting in a class where the problems are simple but get the homework and it’s like I don’t understand it.
I learn more from watching khan academy then I do sitting through a 55 minute class
To true and my classes are 1hr and 30min... tells you that he should build education systems shouldnt he...
+Brian Hunter Oehme Me too.
But I don't have a good Algebra 1 teacher.
i love how he types everything out even,
"let me scootch it over a little bit...."
I think people learn more from khan academy is because he doesn't use the core learning system
Khan plz never stop these videos, bc my teachers r terrible and I understand bc of u!!!
Pretty good except ya kinda lost me when the whole quadratic equation stuff... The worst part is that we went over this stuff in math class
Bro just saved my life bc I have a final today and couldn't remember how to do this
7:40 ya lost me here
Quadratic formula, its when you want to find the zeros or roots of the equation. Its really easy once you get the hang of it
You failed
I lost you at 8:00
+Anonymous User Using the "quadratic formula" you can determin what X is equal to. So if you get a complicated question where your final quadratic cannot be used by factoring, you use the quadratic formula.
Its the quadratic formula, he just plugged in the a, b and c terms into the quadratic equation. x=-b+-sqrt(b^2-4ac)/2a
Is the... method of transforming rational algebraic equatiion to quadratic equation present .??
Right
Thanks .....a lot... i owe you ..my presentatio and assignment ia pres...
+lloyd ancajas ???
Never mind ....important is i am happy with this video
Thank you sooooo much, I'm taking the Precalc CLEP exam and this is soooo much help.
**initiate confused screaming**
at 4:25 I dont understand how you take x^2 + 2x -8 and factor it down to x+4 times x-2. I see were x+4 is because the power of two but i cant figure out how you get the x-2
Lol, same dude. I was confused in that part. I thought it was just me... thanks for existing in the comment section!;)
Here's the explanation even though it's super late hahaha
He factored the denominator
x^2+(2)x+[8]
____+____=(2)
____•____=[8]
^ ^
4 -2
So the factored form of x^2+2x-8 is
(x+4)(x-2)
ETIFETIS: Each Term In the First Times Each Term in the Second. So much better than the old school FOIL, because it doesn't work on trinomials.
i literally love you thank you sm for teaching me this
Hey why on the first example you add 8?
BTW We're probihited to use Calculator T-T
Well when you want to remove the -8 from one side, you have to add 8. That makes it zero, and one thing you do on one side you do on the other.
You have to add 8 to both sides so they cancel out
4:02, it supposed to be x to the power of two +2x+2! Not x to the power of two +2x-8! -2+4 is equals to positive 2!
I learned that shit already in advance math but we never simplfied the square root... We left it as it was bc we werent allowed to use decimals unless it was a perfect square and 113 isnt a perfect square...
You could simplify the sqrt of 113 though
4:41 Isnt x times -2 equal to -2x and not +2x?
He teaches better then my teacher.
what the frack, where did the square root come from?
Haha he turned the equation into a quadratic formula. It’s how you can solve quadratics and you can do it when you have an equation where the first term has an x and is squared, and second term with an x (not squared) and a regular number. When there are usually three terms like that, you can plug in the values (not including the x’s) into the quadratic formula to solve the quadratic.
@@zango3134 I love that you replied to a 7 year old comment. What a legend, thank.
Hi, I have a question I'm struggle with for hours now. Why do we not multiply the denominator by the Least Common Factor too if we're solving the equation? But if we're simplifying an expression, dont we have to multiply both nominator and denominator by the LCF too?
For the second problem how did you get x+4 and x-2 as your least common multiple?
same dude
God bless this atrocity that is math
Thanks, this video was very helpful for me. Tomorrow I'll be taking my math exams and rational equations were one of them.. Thanks a lot Khan Academy!!!
it would help if you explain every step in more detail when you get to end .
But he's not explaining the quadratic formula in this video, therefore, he would just get through it fast. The explanation for solving rational equation was pretty detailed though.
you're awesome man, i love how you teach. thanks!
What do we do if we are not allowed to use calculator
you lose
You can solve it in your head, but if you don't have a calculator you can leave the square root without solving it. You could also simplify the radical expression, unless its a perfect square root. Its weird that you're not allowed to use a calculator though
He just simplified both sides of the equation. He had: 5/35 = 2/14. 5 divided by 35 = 1/7. 2 divided by 14 = 1/7. Since 1/7=1/7, that means that the value of "x" which he put in is the correct one and is a solution.
My teacher does a horrible job explaining things, plus the fact that she just shows us what to do instead of how and why you do it, and on top of THAT it's hard for me to understand math quickly. This really helped. A 42 minute ill explained lesson compressed into a 13 minute well explained lesson
im a trying to learn grade 9 maths as a grade 7 for a entrance exma for my ney school on the equation at 2:53 why did he add the -5x
Teaches me more in the first 5 minutes than 90 minutes of teacher time. Amazing.
I don’t understand. This feels exactly like my teachers explanation.
3:06 does anyone know what to do if you have something like negative X on one side but nothing on the other
I didn't understand what did you do at 2:27
same!
"Hopefully you found that slightly instructive"? more like incredible instructive!
thank you so much for helping the students like me
Fucking son of a bitch made a big ass problem solving this problem
I'm confused as to how you were able to rewrite x^2+2x-8 into x+4*x-2. I know it is possible, but I don't know how you did it. If someone could explain this, that would be great (: @4:26
Hey, I know am 3 years late but there may be others with the same question as you so here I'll simplify it step by step.
Step 1: AC Method
The quadratic x^2+2x-8 is in the form ax^2+bx+c. This will work for any trinomial. It's called the AC Method because we multiply A and C, which in this case is 1 (because the coefficient of x^2 is 1) and -8 and we get -8.
Step 2: Factoring
Now that we have the number -8, we have to find a pair of numbers that when multiplied will equal C (-8) and when added will equal B (2). You can go ahead and list the factors, like 1 and -8 is a pair, or -4 and 2. Once you get the hang of it, you can quickly factor in your head. He saw that 4 and -2 multiply to get -8 and add to get 2, which is why he ended up with turning that into (x+4)(x-2).
Hope this helps :)
@@jah-4 Haha, well thanks anyways! I'm sure it helped others. 3 years later, I can look at the equation and figure it out now, so I guess I am testament to the success of the schooling system.
you were doing swell until you got to the square root parts.....That is so Confusing!!!!!!!!!
that's just the quadratic formula. very easy problem comparing to what's on my upcoming 7th grade algebra honors test tomorrow.
i dont underStand your second problem
you sir are a god
nah dawg this is much easier that i thought after you explained
Thanks, now i understood when you had to use a calculator.
does anyone what he wrote? im lost because all the numbers
Please help bro? this just blows my mind
Now I'm in 7th grade and this is so confusing to me
Learn this stuff early on kids, because learning it at 37 is a fucking pain in the ass
I know this comment will go unseen here, but I'd feel guilty if I didn't thank Khan Academy for the full lesson they just taught me in less than a quarter of what my teacher would spend on the same topic. Thank you!
under x^2+2x-8 how did you quickly get (x+4)(x-2) ..I just checked to see if it breaks down into that, but it was no hesitation for you.
i have to say if math was not hard it would be soo broing
I don't know how fast you could respond to this question but in my college algebra 1 class I'm struggling to understand this equation with rational equations. It's x^2 - 10x + 25/ 3x-5
I always beg my students to determine the domain of rational functions first and without exception.
I've been struggling with this for so many hours, I have a quiz I need to asnwer due today and the way our teacher taught us in our online class, I didn't really understand. Thanks for the vid!!!
In wich video does he teach about adding numbers to both sides?
I love being the first to watch a video :P Thank you fo rall the help and I love your videos!
How you doing mate hahaha
same lol cant belive i scroled all the way to the bottoms
Let's face it were only here because of class
4:31 Where did the 4 come from? Sure, it’s on the left side but how did you just pull it out of the right side?
i have a test tomorrow and i’ve been pulling an all nighter just to get one question right. came to this and got it in less than 10 minutes
I know the answer to (1/x) + 1/(x +1) = 2
It's x = 1/sqrt(2), -1/sqrt(2)
this video didn't help me i learned more in the 5 minutes i stayed awake in class today than in this entire video
what is x minous y, over 4, plus x plus y, over 3 = 1 ,if you have to resolve for y
This was more less of a video explaining the quadratic formula.
why dont you make questions in the description to ask students, and then in the next video put the answers
you do realize this video was made in 2010, right?
@@seadawn8559 nope
I learned more in this video than the entire unit my teacher taught on this for 3 weeks
why use negative 5 to cancel
For the future people cramming their Algebra test (like me hehe) and scrolled down the comments section to ask where the hell the square root came from, it's because he used the quadratic formula to factor the equation. And you SHOULD know what the quadratic formula is, since you should've learned that from solving quadratic equations.
Lol same here
bless khan academy
you dont understand how much i love you, my teacher is probably 100 and can barley explain to me anything. you made things so clear to me, thank you.
san nang galing yung 5x tol?
Omg thank you so much i understand it better thx!!!
Why did he add the 11 ? Shouldn’t it be 11 - 10.63 ?
@cyclone2876 wtf no its not. he uses a usb drawing pad
Thanks sir
WAIT! pleassee! How did it became minus 5x (-5) for both sides? at 2:53 ??
Why can't you just cross multiply?
Omg thank you for your guidance.
thanm you for this. its very helpful
@zacrichards1
maybe this is photoshop (using a graphic tablet)
Just quadratic formula
Thank you!! This helped me with my hw.
kahn you saved my life long learned
I better hope I get better at math with this.
Thank you.........
On 8:00 can't you also factor that?
I'm so dumb 😧
im confusion
Lol listen to this at half speed.
I love you omg helped me so much 😭
Thanks for the explanation