Quadratic Inequalities

[8arry94]

You helped me grasp this in 10 minutes whereas my algebra teacher wasn't able to over several classes. Thank you.

[nothisispatrick68]

If you don't shop at Wal-Mart you're a loser!!!

[nothisispatrick68]

Wal mart is a wonderful store to buy all of you whole foods and do your christmas shopping at the same time!!!

[nothisispatrick68]

Shop at wal mart!

[nothisispatrick68]

shop at wal mart!

[nothisispatrick68]

im a scatman



[nothisispatrick68]

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[nothisispatrick68]

hey guyz this is dylan commenting on the video

[BestCoolGuy22]

I came across the problem x^4 - 25x^2 + 144 < 0

How would I go about solving this?

[redjr242]

@BestCoolGuy22

simply replace x^2 with y into the equation then factor, solve and change the y back to x^2

[ricado7535]

@BestCoolGuy22 square root it so; x^2-5x+12<0 and then work from there

[MrDaghma]

guys I think that there is a mistake !!

Who agrees . and What is that mistake !?

[starfish91804]

you're such a dork!!!!!!!!!!!!!!!!!

[musicluva13579]

i don't understand 7:50

[tereypil]

Understood...

[gautamv8]

THANK YOU!!!! 

[20raeali12]

Thanks so much! This is more helpful than anything I learned in 5 years of math

[kinglynx]

very good but please get a tablet!!! :P

awesomeness!

[TRFriendly]

Well thanks for the lesson. Time to go jump off a building....

[iMintzGummie]

You are a BEAST <3 [No HOMO]



[LinaCan]

math makes me block completly.... how am I EVER going to get this stuff?? any tips someone??

[derp12347]

@LinaCan Watch more of his videos. :)

[Pardue52]

Why does part 2 of this video have more views than part 1? Apparently the majority of Youtube users arent at first grade level yet... because they cant count the sequence of videos.

[SamoyedLucy]

@khanacademy My teacher showed my class this for Algebra 2 and she showed a parabola as the graph rather than a number line. Why?

[TheTranceWhale]

Are the colors on strike, Sal? :)

[UnitedPebbles]

Hey anyone ever take Q.A.? look at the magnitude of things and everything else is negligible! especially if the coefficients under square root is a negative number!

[UnitedPebbles]

He sounded like the President!

[weatherman1994]

Incredibly well-explained. However, it might be simpler to teach this lesson using a sign chart (as not every complex inequality is going to be as nice as these factorable examples).

[crucio6199]

You explain it so beautifully. Thank you! :)

[picthebudgie]

Dude you rock my socks!! Chur heaps!

[1995a1995z]

I dont understand how you changed the -3 and -4 into +3 and +4?

[Optiyay]

@1995a1995z

7:21 .I wouldnt like to delve into what Sal says from 7:37, but the bottomline you need to understand is that when (x-3)(x-4)<=0, ie: their product is a negative value, then (x-3) and (x-4) must be of opposite signs. ( -ve * +ve = -ve, -ve * -ve=+ve,  +ve*+ve=+ve) . hence, it isnt just changing them into +3,+4 ,(see from 8:19), carefully. I hope you understand it :)

[1995a1995z]

@Optiyay ow right I understand, so when its a "- and a -" it becomes positive. and when its a - and + it becomes negative. Yeah thanks man :-)

[sgacz55]

ID PREFER YOU ANY DAY OVER MY TEACHER!!! THUMBS UP IF YOU GUYS AGREE?

[sgacz55]

ID PREFER YOU ANY DAY OVER MY TEACHER!!!

[dmonst3r]

I just kissed the screen! 2:42 onwards you just solved one of the biggest mystery in my life. HOW DO I WRITE THE RANGE! I Love you man!

[Sylvanas17]

ur freaking awesome x3

[SuzeRetardation]

thankyou so much

[abcsmedotcom]

here's the graph showing (x-3)(x-4)>=0 is possible.

wolfram alpha dot com /input/?i=%28x-3%29%28x-4%29%3­E%3D0

this shows that the first solution is possible.

Could they just be roots?

It could be possible that your logic is valid, but not cogent. You may have not accounted for something. The link has a graph, and a number line.

[abcsmedotcom]

@abcsmedotcom

because as a quadratic inequality,

the function may still have roots and different corresponding x - y values.

Anyone's insight is appreciated.

[flarefiragax]

u sir, are a legend.

[deathblade68]

@flarefiragax

Precisely the case

[deathblade68]

@flarefiragax

[radiator0505]

How do you get these into the form n<x<y?

[TheElmo1231]

thanks this really help me

[CocoCrispy22]

this is more confusing then my teacher taut but in the end it makes more sense

[Cross3dPoisons]

why the dislikes?

[Xplosiv3s]

@Cross3dPoisons They are probably from other people who post videos but get less views lol

[nghi1350]

Solving by discussing the signs of the 2 binomials consumes too much time. During tests/exams time is limited. The best and fastest way is to use the number line and the origin as test point.

[DarkDragonSlayerGirl]

man, this is confusing. too much numbers make my head spin @.@

[utubsdum]

@DarkDragonSlayerGirl lol they're not even numbers they're letters

[carlitoxxwwe]

@DarkDragonSlayerGirl same here!!!

[ChinitaPhuongVyDinh]

Is there a video on how to use the squiggly line method to solve a quadratic inequality? that would be extremely helpful!

[reallyflasshy]

woah , this tecnique is fucking awesome

[1080portal]

k, i get it now thanks!

[SoullessTech]

omg i wish my teacher would teach us this crap before he gave us homework on it >.>

[furyofnasa]

@SoullessTech lmfao

[Pardue52]

@SoullessTech Right? I got this for homework over the weekend and I was supposed to learn it from my book. So I am blowing that off and learning off of Youtube. Similar predicament anyone?

[gregjones91]

i think most people understand the basics of it but i need help learning how to do them in a sense of difficulty

whereas x^3-4x^2>0

^ is the exponent to the number after ^2 squared ^3 cubed ....

[ndog33]

Sal, i hope that i didn't say something bad, because I forget wat i said, and i now get it. thanks

[GDATERRY]

So wait, we don't need to draw a stupid table everytime we do these questions? Wow. Thanks saves me time and gave me some intuition.

[p1n0yXer]

@GDATERRY you can imagine the graph in your head

[brandiceMofucka]

Once again! i've learned and acheived good marks because of your tutoring :)

[YukonTrooper]

It's nice to see this done without having to find negative or positive quotients for each interval.

[uglymug211]

Having all the terms on one side is called the Null Factor Law. According to my Maths 10 B teacher...

[rosered07]

Thank you so much! I get it now! :)

[clixsyt]

I learned this in 7th grade but forgot so thanks.

[elementoxygen]

Thank you so much! You helped me a lot. nicely done. Your a really great teacher. I have almost seen all your videos and have learned a lot from you d:D !!!!!

[gimmeurdosh]

standard form is like 2.6x10^4 instead of 26000

[Paulorific]

That's scientific notation.

[gimmeurdosh]

Well we've always been taught it as being called standard form.

[Paulorific]

It's *a* standard form. A "standard form" is another way to say "the way it's usually done".

[252727439]

Thank you so much! i also have a test coming up tmr.

i can't concentrate in class because everyone talks too much x_x

[Winsunn307]

You are a great teacher.

[RALMAR9]

agreed

[chrisbtoy]

Amen people

[majorkeybaree]

at 7.36

"they have to be of different signs"

is this cos we are dealing with 0,

ie, the answer must be less than 0, a - number??

[idster7]

@majorkeybaree yes.

[abedbae]

wow this cleared it up for me.

[27dimensions]

nicely done. I'm a sophomore, and am in the Math Honor Society at my school. Your video taught me how to be a better teacher. thanks a lot!

[screamingsarcasm]

Thank you so much! Math has never been a strong point of mine and no matter how many times I looked over the examples in the book, it seemed like they were getting the answer from nowhere. Now I see how simple it really is if you just look at the possibilites logically. Thanks again! You're wonderful for making this seem so simple!

[Jethos]

Alright now I get this. My teacher is lame. He doesn't teach me how to do this at all. He just chats a little on it and says to read the book.

[Brian626]

thanks, my math classes barely taught me any of this stuff... its great to learn it

[TheTerminator1]

What you are doing is great! You really helped me with last minute understanding before a test. Thanks!!!!!!!

[darkhawk362]

i need to solve this problem: 3.7/26.00

i need help.

how do i change the 3.7 to a whole number?

and what happens to the 3?

[idster7]

@darkhawk362 you're trying to divide 3.7 by 26.00? just move the decimal point over once to the right for each term: 37 divided by 260.

[desoan]

umm can someone tell me why a set of numbers cant be less than 3 and greater than 4?

[khanacademy]

any number less than 3 is also less than 4 (so it can't be greater than 4)

[desoan]

oo kay i just read it wrong lol thanks for clearing that up

[dzkzk]

He explained it very good. Similar to Absolute value equations just a little bit more thinking. I understand it completely=)