Parabola Focus and Directrix 1

[epiclaxbro]

really helpful

[ChiRhoFTW]

This video would be great without all of the popping.

[acevedohiram]

The one dislike is probably a crappy high school teacher

[tysonoboyoboy]

Honestly, I had no idea what he was doing. Oh well....

[KahnMentor]

@tysonoboyoboy Well, watch some of the others he made or try other vids on Parabolae. It might help make the connection.

[dxl1key]

Hello Sir! Keep up the good Job! What is the name of this blackboard and where can I download this?? THX!!

[AutumnxDay]

@dxl1key You click on the "show more" button below the video and there should be a download link there...

[jaynaiyeshia]

the best illustrator i found online

[TheSpyker123]

hahaha how can you blame his videos ? why is your speakers broken

[Dgbug3]

Why are all of your videos muted?

[brandoncueto]

@Dgbug3 check your volume, go to mixer, check if you muted firefox or whatever browser you are using

[SuperTakeoff]

@khanacademy how do you solve (x-2)^2=4y

[0RPH3U5the666r3ml1n]

become my math teacher? please?

[paulceltics]

100th like

[khanbhai197]

how b-k is cancel out????? explain

[darnchinese]

great video, can you not do subtitles. it is somewhat distracting and i can hear you perfectly well

[zigzag747]

@darnchinese just turn it off. Right below the video, make sure the CC is grey, not red, and they should be off.

[MrPlender]

Just incase people want clarification Sal has made a mistake. He should say times by 1/(2b - k) at 10:30 not divide.

[vkgoku2012]

bro so all ur doing is matching stuff up after u write a long expansion tat seems like elementary.

[0RPH3U5the666r3ml1n]

@vkgoku2012 yea but isn't that the point, to break more complicated math into its fundamentals so that it's easier to understand?

[elisprague]

i wish i could get my mind around this stuff, it seems so fascinating, but i only did geometry and i was done lol

[Bangelfan22]

How did you get the 2yb and 2yk?

[mrinehart93]

If only you were my math teacher... I would actually understand this!

[tectquix]

PHONE IS REEEENNNGGEEIINNNG OOOOOOOO hahahha jast keeding AWEOMSE ld

[bolarinwaJR]

thank you for doing this!!

teachers should be like this!

[Taowhr]

Don't you mean "multiply by 1/2(b-k)" and not "divide by 1/2(b-k)"?

[TheMazurka]

If there was a 'double subscribe' button for this channel, I'd click it.

[aeropostale]

this is very helpful although its very confusing. if i had to do something like this on the test then i'll be so screwed

[Plartus]

thanks helped allot .

[bhaskarpanerihotmail]

lol..... "radicals are not good"...... "well I don't want to make any social commentary"......funny joke

thanks for the vid

[MustBeFiend]

i love how it takes class at school one hour to teach this and this vid taught it to me in 15minutes...and clearer.

[hanko2001]

Arbitrarily replacing (x-a)^2 with (x-v)^2 is poor form, no?

[woo216]

if this guy was a teacher then his students would be getting very high marks because he explains the reasoning behind math which i think is of highest importance thankyou for this video

[anotsofamiliarface]

@woo216 and that's why most other math teachers suck epic ass. they don't explain shit.

[readthesecomments]

"so the first thing we can do is get rid of the radicals. radicals aren't good...well, i dont want to make any social commentary."

hahhahha you're funny

btw thanks for making all these vids!

random, but how do you make money from this? or do you have a different job?

[dubaipete]

"Divide by one over.." is in fact the same as "multiply by...". Correct way to say it is simply "divide by..". Don't mean to split hairs but could cause confusion.

Regardless mate, you are doing a fantastic job! Thank you for helping to make mathematics understandable and fun!

[Jtking3000]

i think around 1/5 vis i go on of yours your phone rings. just turn it off!

[Budisawsome]

Our teacher did about a 10 minute thing on this. Thanks for clearing it up khan.