Added: 5 years ago
From: khanacademy
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  • 3/x=5, x=3, i am an algebra geek.

  • You make math so FUN!

  • @1989Firecracker

    I'm marking your post down for racist spam.

  • @1989Firecracker

    Also, you're a slav, who hitler kiled all the same.

  • @1989Firecracker and you are a very foul mouthed racist no-life jerk

  • Now linear equations are getting too hard for niggers.

  • @1989Firecracker racist

  • Okay I got a question how do you know which side to subtract from? Lets say i've got 6x+6=15x+30. Should i minus 6x and add to 15x or minus 15x and add to 6x and why?

  • @Richard133t IT can go either way, but I suggest you do 6x-6x+6=15x-6x+30, because this way your coefficient wont be negative if. My teacher told me to subtract the variable to the number with the largest variable (Sorry if that was confusing, what I'm saying is, since 15x is bigger than 6x you would "get rid" of 6x). Hope this helps you :D

  • guys he multiplied by 1/5 to get 1/5x5/1 which cancels out to make 1x which is x.

  • why do you multiply by 1\5?

  • I personally dont like how he does the times 1/5. I would just divide by 5, its a lot easier. And when he's try to cancel out one of the x's on one side he always subtracts the bigger number and thats a lot more confusing and harder to me. If I had 3x and 8x I wouldnt subtract 8x, that just makes the equation more complicated.

  • I don't understand how he decided on 1/5.

  • This probably is my least favorite video in your math series. Seems like there was much less explanation that previous videos...

  • very hard to understand this your other stuff...

  • Hard to understand...

  • 0:40 Wait, why would squaring "X" make it cancel itself out?

  • @EnemyBikeCo i agree.

    why do you cancel out.

    there should be an explanation on why. these are detractors from learning because we just automatically cross out with out a reason.

  • @erule92 'x' is on the dividing side of the fraction...so he multiplied it by x to cancel it out. It cancels out because anytime you divide and multiply something by the same thing (in this case x)...you get 1 (which when multiplied or divided keeps the number the same). So like if you have the fraction 4/5 and you times it by 5...the 5's cancel out and you get 4/1 which is 4. He wanted to cancel it out because having x in the denominator is useless to solving the problem. It needs to be alone.

  • @vicksoma thank you!

  • @EnemyBikeCo He didnt square x. Since it was in the denominator (the dividing side of the fraction) he multiplied it by x. And did the same to the other side of the equals sign to keep it equal. If you divide and multiply by the same number they cancel each other out and make 1. It's like adding and subtracting the same number gives you 0. In this case it was divided by x...so he multiplied by x to cancel it and make it 1 (and anything multiplied or divided by 1 stays the same) so he got 3.

  • I just love it how he makes it awesomely easy and then he's like "let's do another one" :D

  • I'm in 7 th grade and this stuff Ismso easy and I want to do this in math and start learning more advanced stuff any advice

  • @MrSethsiPodz Not sure about algebra. But if you like numbers watch this. "Speed maths- Multiplying without multiplying". Click on my username and check the vid. Cheers.

  • These videos are really cool and helpful!! I wish he was my teacher......

  • just wondering, why does it say "6x packs" at 3:42?

  • Comment removed

  • i wish you were my real teacher

    

  • freakin awsome

    

  • start from easy ones

    chapter by chapter and give a test at the end of each chapter

    provide answers with explanations

  • Comment removed

  • Mr. Khan your awesome! Your an awesome teacher and i'm finally beginning to really understand how some of the more difficult Algebra equations work.

    Thanks alot!

  • Like many others have expressed, I wish you had been there instead of the indistinct mumbling, arcane rules, and back of the head I was provided with in my introduction to Algebra,

  • can someone explain why he's used x+1/1? i get the x+1 bit, but why the 1? why not x+1/2? or even 3? one of the reasons maths throws me is that i just don't get that sort of arbitrary decision, and it's really frustrating

  • @Lilandriel one over one (or 1/1) is the equivalent of 2/2 they both reduce to equal one (because one divided by one is one and two divided by two is one) He just wrote it as a fraction because while working with other fractions it makes it easier to compare the two, thus he could've used 2/2 also but 1/1 is easier to use ^~^ hopes that this helps

  • @SilveraLordz  actually, I think that does help! thanks for taking the time to explain :) much appreciated

  • @Lilandriel Welcome ^~^ I'm glad it helped :D

  • Either 24 or 25

  • Actually the X should be negative.....does this mean that for example -1 . -5x = x and not -x ??????? 7:00

  • if you were born in 1986 and its 2011 how old are you?

  • @Justcool11100 Probably 25

    

  • yayaya!!! i got it!!! :D :D :D

    wow, that was extremely helpful...i'd trade my math teacher for him any day.

    (:(:(:greenplanet:):):)

  • y does this have so many views lol

  • does he get paid?

  • @nube1oscuras lol he gets paid from bill gates because its so awesome

  • It was not explained how "7(x+1)" turned into "7x+7" .( we don't know what "the distributive property" means). Please explain.

  • @minivanjack you multiply both of the numbers in the brackets by 7, then you take out the brackets.

  • wat? why was i not told this?......and how'd i get into IB if i can't even do problems as simple as thiis?? .....although this is very helpful...oi...

  • Why does the 5 turn negative?

  • After looking and looking I think I get it now, but using fractions makes this a nightmare. I am not american and fractions where gone over little in school and never used in real life. I do love decimals.

  • I feel as if this video jumped over several explanative steps as the earlier videos did. I don't understand how and why the equation works. Seems to me that this is more for refreshing rather than a learning from the ground up video. I have no previous experience with math like this. The earlier videos explained every step though and made it easy to understand.

  • Seriously this is fucking magic, maybe it's because im older and i have a clearer mind but this seems so clear to me now, it's so obvious. I have always been a bad math student I could never understand it and suddenly now its so easy.

    My whole college direction was consciously chosen to avoid math in any sense because of my giant ignorance in the field and here I'm learning it with ease.

    I swear If i had this 6-7 years ago it would totaly change who i am today and what I do.

  • @colloredbrothers Thank you for inspiring me and I'm 15 years old and Wish me good luck I'm trying to get to the calculus level.

  • @colloredbrothers U couldn't solve linear equations before college? How sad is that, I could solve this shit when I was 3.

  • @Pr3fixProducts

    Good for you, Iv never beeen a math person.

  • @Pr3fixProducts Then why are you on this page then? Is it your hobby to review elementary mathematics on youtube in your spare time? Because I've always found that going through youtube and goin back over the alphabet was a real hoot myself. Save your bullshit trolling for a Bieber video you spineless little fuck.

  • @MarcusTexaco Browsed through the khanacademy's tutorials, stopped by to insult idiots who can't understand simple math etc. And you just recognized yourself as one of them, I feel sorry for you.

  • @Pr3fixProducts @Pr3fixProducts Lol I'm a philosophy-mathematics double major at osu doing my thesis on the meta-mathematical implications of additive prime number theory but apparently I don't understand basic algebra haha will you please teach me all knowing one?bahahahahhaahahha

  • @MarcusTexaco If everything of that was true you wouldn't be viewing videos such as this one, also you wouldn't be talking like 13 years old kiddo that just got on Internet and expect respect from everyone and when you actually get pnd rage. Oh and, I am not all knowing one, as call me , that is pratically impossible as some events that I don't have knowledge of would require my presence, at all times and and places which is impossible. Mr Philosopher that can't use simple logic.

  • @Pr3fixProducts Hahahaha someone seems quite upset that they were made out to be an ass in front of the entire youtube community. And sir, if you must know, I was sifting through algebra videos in search of advanced linear algebra pertaining to determinants but upon seeing your asinine comment, I found it necessary to insult you as well because you are an insult to the intellectual community. You should be attacking persons not trying to better their education, not the other way around. But as

  • @MarcusTexaco Actually, it's you that was upset otherwise you wouldn't call me "spineless little fuck", now would you. It's quite funny how you posted 3 long comments, it proves that it got to you and that it is true. I also find it very funny how you defend and explain yourself in every single sentence, someone's insecure? And please, you're insult to the intellectual community just by being on the internet. You never gave me any valid argument whatsoever. Oh and I won't be point

  • @Pr3fixProducts it is quite apparent that you are simply an ignorant fool who gets his rocks off by insulting others, it seems rather pointless to continue this conversation any further but I do want to make one last suggestion, if you believe my last epistemology related comment pertaining to you being an "all knowing one" was serious and not sarcasm, you have some serious social ineptness and

  • @MarcusTexaco pointing fingers, but you're the obviously one who has no idea what's he talking about, or for short 'ignorant'. And, I understood what you posted was sarcasms, I just wanted to humiliate you a little bit more because of your stupidity, you know I find it funny how only unintelligent people are the most arrogant one. That is the funniest part, you can easily manipulate them and make them do whatever you want. You're perfect example of that.

  • @MarcusTexaco So please, stop humiliating yourself in front of whole YouTube community, which you previously accused me of, and actually do something useful. Go read a book, do some Elementary School math or whatever your brain finds extremely challenge because that way you will improve it and hopefully next time you argue with someone post something of value which won't show how insecure and unintelligent. Wish you good luck. =)

  • @Pr3fixProducts I suggest seeking professional help. But I'm not going to waste anymore time on this pointless conversation. Just continue to insult others for arbitrary reasons and see how far it gets you in life.

  • Can someone please guide me through solving 3x-2/2x+3=4x+4/2x-2? Or any other equation that has the variable in both the numerator and denominator?

  • what does he mean by level 1,3 equations?

  • why do you divide in X+2/X+1=7 shouldn't you multiply?? Someone please explain

  • thx

  • bruv my head hurts

  • Bravo!

  • Why do people have to say "No Homo"? Just leave it at "I LOVE YOU!" And we'll all completely agree!

  • 8x + 3x = 5x.

    Since -8x is more than 3x then you have to 8-3 <- thats just an imagination of how you should do.

    So....

    -8x + 3x = 5x.

  • would be perfect if ; you were to show every step made including reducing etc

  • i dont get this :( where do you get the (X+5) over 1? and why do you have to multiply?

  • @waaathaaa Since the x+5 is in the denominator you have to MULTIPLY to get it out of it's place as a divisor. If you think about it, Multiplication and Division are merely the opposite of each other. Yin and yang. The same is true for Addition and Subtraction. So to get something out of a divisor placement you must multiply it. To get something out of a quotient placement you must divide! I hope that helps!

  • on the equation 3over x +5 = 8over x + 12 How did you get 8x +40 over x +2??

  • @13sophiecat oooo.... idk too. i hate math.

  • @13sophiecat

    8over x+2 not 12. I'm geussing thats why the outcome doesn't seem logical.

  • i started liking maths because of you :) thanks

  • @ewenson111 that's using the distributive property.

  • why not subtract 3x not 8x?????

  • @ekamjot2209 you can do it either way. Khan felt like doing it the harder way..

  • @ihavemonkeysinmybutt thanz but i know

  • (x+1) times (x+2) does not = (x+2) i dont get it

  • @ewenson111 ACCORDING TO (X+1) TIMES (X+2),you would need to first multiply x (from first factor, (x+1)) into x and 2 (to the second factor, (x+2)).Then you should multiply 1 to x and 2.therefore u will get an answer of : (x square) + 3x + 2

  • You are a champion. Needed a quick refresher course for linear equations for an upcoming test. Couldn't find (x+a)/(x+b)=c anywhere else online.

  • i still dont get it:(

  • wow i dont get this at all

  • thanks man

  • If you want to become good at Math visit my channel: ( Mathmatchpoint ) In my videos I'm going to teach you Math the “EASY WAY”. I'll teach you all Math topics; from the basic to the advanced topics. You can watch my Math videos in order by clicking on Playlists.

    Mathmatchpoint

  • why don't you teach them cross factorization much simpler???

  • @kolson13069

    yeah instead of multiply the inverse....

  • @deppressed1

    I'll send you 3 dollars, you divide it into 5 dollars for me.

  • oh jeez, this is where math gets complicated. i'm stuck.

  • Would you always want to do the right side first?? EX in the second problem he subtracted 8x instead of subtracting 3x?

  • @Chequelito14 it works either way he did that because he didnt want to end up with a -34 on one side

  • How the hell is 3 divided by anything equal to 5? You can cut it into 5 pieces, but its not equal to 5. Its a 3, you're missing 2. Math sucks, i'm going to drop out and live with my mother.

  • @evilsinzy It's O.K. Buddy, hit me up. We'll go fishing, have a race with shopping carts. and smoke a bowl in the Jungle Gym...also, if you do one thing you do another...also FUCK MATH. ...also motherfuckers went to the MOON...wat do?

  • @gishikin

    my mom says hi

  • @evilsinzy Lol, I got it. :D Basically, -8x + 3x = 5x.

    Since -8x is more than 3x then you have to 8-3 <- thats just an imagination of how you should do.

    So....

    -8x + 3x = 5x.

    Your welcome.

  • I almost wanted to say that is 34/-5 not -34/5 but, actually the result is the same :)

    P.S. Great lessons!

  • If you cross multiply the last problem, it'll save you lots of trouble.

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  • Is there a list to show what the next lesson in line that would come after this... What lesson would normally follow if you were to take this in school... I am trying to find it but I don't see anywhere that shows it???

  • No matter how many times i watch it i still cant get it.

  • we understood

  • your not explaining what u want 2 be the subject

  • Why not just cross multiply and save all the time?

  • @RobinhoGreat25 thats what i was thinking after i watched him solve it all the steps just make me confused

  • what if you cant find a denominator? ex:4x-5 divided by 3 + 2x+7=4

  • i'm jealous

  • Oh man!!! You are too fast!!!

    Why can we write 5x=3 if previously it was 3=5x?????

    Otherwise, thanx for these lessons. I just cant see the point of maths...

  • @Kuzmorgo

    5x and 3 are interchangeable, because both sides of the equation are actually the same number, written differently. Hence, 5x = 3, and 3 = 5x.

  • @Kuzmorgo "Otherwise, thanx for these lessons. I just cant see the point of maths..."

    yr currently on a computer that was programmed by the use of mathmatics

  • @Kuzmorgo "I just cant see the point of maths..." you are currently using a computer that was programmed by the use of mathematics.

  • I missed class on linear equations. I picked up level 1-4 in just a few hours, easy.  took notes. I won't be behind when I get back to class tomorrow. He makes it interesting. Big thanks to the youtube instructor. -tru64art@yahoo.com-

  • @ohyeaimtruth whats with the email?

  • Isn't it better to teach the student to move to the other side, without having to multiply both sides? Probably not, but do think about it for the HD refresh.

  • i though algebra only went up to algebra 3

  • if there's super man ,you're my megaman....

  • Can someone explain why you times by 1/5th? That's never explained where that 1/5th comes from.

  • i'm homeschooled. and i watch your video's almost everyday just to help me out a bit since i basically have to teach myself. i would literally pay for your tutorials, man. :D

  • CramMaster is shit compared to KhanAcademy

  • No Algebra: Linear Equations 5? :'(?

  • what is the precursor to Algebra that I must understand before learning Algebra?

  • Thanks for showing this video in Youtube, study in here or your video is much better than in college. And very easy to follow, wich step I don't understand I can just reviwe it. Again than you very much.

  • Multiplying something by 1/5 is like dividing it by 5 right?

  • @gorillaking37 Yes. basically the number 1 was left because it's useless.

  • You are a great Man. Really appreciate what you have done.

  • i wish you were my math teacher

  • 4:41 & 4:48 => that's what happens when people think too hard about something... they tend to forget the other little details.

    when taking tests, don't forget to breath and fulfill your brain with enough oxygen.

  • @jasanpahaf - No, that’s just you being too stupid to understand elementary algebra. 

  • by watching the first 4 of these videos, i have learnt more in this space of two hours then i have since the start of term one. its like. half way through term 2. thanks alot.

  • omg

    thank you soo much <3

  • wow this teacher is amazing

    i think i love you (no homo)

  • Thxs bro, this totally helped me out, I was stuck on 2/y+3 + 3/y-4 = 5/y+6 , but when i saw 5:00 I understood what i was doing wrong, it was the way i was multiplying it. Was doing 2(y-4)(y+6)= 2y-8(y+6) , instead of 2(y-4)(y+6)=(2y-8)(y+6). You overlook the simple things sometimes.

  • where did the +40 come from?

  • @ChildHoodHorror Nvm he explains where i got lost on the next line

  • @ChildHoodHorror

    distributive law

  • @ChildHoodHorror

    8 times 5 is 40...?

  • @ChildHoodHorror Its called multiplying out the bracket. 8 times X = 8X and 8 times 5= 40 (because the number on the left of the bracket has to multiply each term inside the bracket seperatly then you can remove the bracket, thus simplifying the equation.

  • @ChildHoodHorror At 5:42, he used the distributive property by multiplying not only 8 by the variable x, but by the +5 that was in the parenthesis with it.

  • @ChildHoodHorror  Distributive Property. 8 times x = 8x 8 times 5 = 40

  • @ChildHoodHorror distributive

  • @ChildHoodHorror you dont seem to understand linear equations :P

  • The first equation, was that a linear equation? If so im going to transfer out my class. The teacher I have seems to think those type of equations aren't linear.

    I trust in Sal he's the man and I would expect his title of linear is correct.

  • I'm 50 and finally going to college. I put 2 sons through college and now it's my turn. I haven't had an Algebra class for 33 years. Your videos are a lifesaver as I prepare to take the entrance placement exam. Thank you! I wish you could work the algebra problems on the CPT practice test.

  • Comment removed

  • @jellofast

    agreed, i learn much more in college, due to less class time. The way high school was set up, it would make me want to sleep in class.

  • Khan thanks so much!!!

  • for the first part ofthe vid:

    just say multiply by the recipricol thats easier

  • I nearly got lost when I heard 40. XD

  • @RANDUMBeva

    people are in school too long & they lose focus. european students spend less hrs in school than here but they have higher scores

  • As much as i love my math teacher, you are waaaaaaay better at teaching math.

  • WHAT? see if you pass my class now.

  • Khan I love you (NO HOMO)

  • @Dagangstapapi

    3(x+2) = 8(x+5)

    3x+6=8x + 40 < you multiply 8 by 5 which equals 40

  • On the 3rd step: Why choose to take minus 7X from the left side?

    Couldn't you choose to just munus 1X from the rightside?

  • From what I understadn, you subtract the number that is furthest away from x, so since 7 would be the furthest number, that is the number that you should subtract.

    I'm pretty sure that's it, but you might want to talk to your math teacher about it.

  • i have to say i've been watching these videos

    my teachers at school arent half as good as you

  • how can you check a fraction over a fraction

  • in the first example how can 3/5 be equal to 5?

  • @ligener I got X=5/3 WTF?!?

  • @TheWTFers i know the answer is right because 5 times 3/5 is 3. my problem is when i check. how do i write it down

  • @ligener 3/5 is the same thing as 3 divided by 5 so really this equation would be 3 divided by X = 5.

    To check just plug in the x, so 3 divided by 3/5 and it should equal to 5. Check and let me know.

  • you teach better then my teacher :O

  • Shouldn't the added x be -x to be able to cancel-out the +x

  • Very strait forward love the videos

  • Love your videos Sal, you're helping me so much i feel like i should pay you. :)

  • Comment removed

  • 0:50

    So if you were to multiply a fraction by X does that mean you do it like X over X times 3 over X like in this?

    I don't quite understand how they cancel out there.

  • this is great