cramer's rule, 3x3 linear system

[680540]

I think Dx is 5 not -30.

[Mik3y243]

Thanks A lot!



[dancevuna]

Oh I love youtube for things like this. You are not an angry Russian lady yelling at me and I got it and still feel smart, whereas when she is trying to say things I feel like a 1st grade kid all over... not fun. But you made me smart. :)

[ConnectingRod911]

Great upload! I have never had that explained to me and I am a senior in engineering. Very concise! I Look forward to watching more of your uploads.

[XCeazyX]

Ah, very helpful.

[EJdaTCBman06]

Amazing refresher for my midterm exam tomorrow, thanks a lot!!!

[JohnnyBoyVids1]

as soon as she said "you can take the Diii" i went from being in college back to highschool.

[GethinLlewelyn]

Brillant, so easy to understand now!



[amehunt1]

Awesome.............really clear and easy to understand. Thank you

[wmschroeder]

Thanks for the help!!

[amaze2n]

saved me, big thanks

[ramiBudemaris]

perfect simple video, thank you for the upload.

[XSweetXAngelXAnimeX]

hold on how do you got -15,-30,120,-15???

[MrTfalls]

@XSweetXAngelXAnimeX You need to know how to evaluate determinants.

Check out any video about it, then it'll be clear.

[Mobie3331]

I believe Dz must equal 55

[clrc333]

isnt d -14 please comment i have test tomorow and dont see how i got d wrong -19 +5= -14

[robichaudd]

@clrc333 Here's how to get D for the 3x3 Cramer's Rule video. The same process can be used for Dx, Dy, and Dz.

For D, expanding around the top row of 1,1,1 we get

1(-16-3)-1(4-1)+1(3-(-4))

1(-19)-1(3)+1(7)

-19-3+7

-15

Hope that helps :-)

[clrc333]

@robichaudd

thanks i got 100 on the test!

[robichaudd]

@clrc333 awesome, way to go!

[jazzyjimmy83]

@clrc333 haha tomorrow is mine

[mistakayz]

i think the answer for D is -14

[roidz17]

Marry me!

[Scrapsies]

you've obviously done many of these to find out the tricks. Thank you for sharing your tricks!!!

[Nawrejin]

thank you very much :)

[TheOrangeFondler]

Thank you! Good explanation.... weird hearing "zee" though haha

[ews773]

Thanks!

[mdedios3517]

How do you get the -15 ,-30, 120, -15 I keep getting lost there. Help asap please!

[danwat1234]

Kramer is one awesome dude with the crazy hair and his crazy habits.

[robichaudd]

Here's how to get D for the 3x3 Cramer's Rule video. The same process can be used for Dx, Dy, and Dz.

For D, expanding around the top row of 1,1,1 we get

1(-16-3)-1(4-1)+1(3-(-4))

1(-19)-1(3)+1(7)

-19-3+7

-15

Hope that helps :-)

[Uzorc1]

You Need to explain how you got -15, -30, 120, -15, ..Its necessary

[94ufcfan]

mannnn you need to explain how you got -15?

[robichaudd]

@94ufcfan I had the D values done out ahead of time. For how to evaluate determinants check out my video on 'how to evaluate a 3x3 determinant' at my channel.

[94ufcfan]

@robichaudd oh okay thanks for the help! appreciate it very much!

[triplemango101]

THANK YOU SOOOOOOOOOOOOOOOO MUCH!

I spent around 3 hours trying to figure out how to do these types of problems. You made it SO easy for me to understand. Please, continue to post videos on Algebra 2/Trig. because you are AMAZING at explaining.

Thank you once again for this!

[coreyownz]

lol I love youtube

[TARANUS123]

thank you sooo much, you explained it so well and made it look super easy!!! thumbs up, now to get an A on my final,,

[cANDYman61116]

Does anybody know how to prove cramers rule by elimination or substitution using this setup below (no numbers just variables)

ax+by+cz=j

dx+ey+fz=k

gx+hy+iz=l

[manishy1]

@cANDYman61116 Erm, I think you'd simply do the same method, via Gaussian, perhaps, and then repeat it via Cramer's and compare the results? That might get you a B as far as points of understanding are concerned (in australian standard mathematics, where we've abolished marks for some retarded reason, that's practically equivalent to 1 and 1/2 marks for a 2 mark question)

[lolololort]

imo it's bad to learn these 'how to solve' vids. It's better to just remember

cramers rule: A^-1 = adj A/detA => X = adjA*B/detA => xj = det(Bj)/det(A)

with Bj being A with col. j replaced with B.

But Cramer is very inefficient anyway

[rubysymms123]

Thank u so much. I have to do a math packet over the summer for a grade and I was at a loss until I found your channel. Thanks so much

[Jenice923]

GREAT!

[mastamind9682]

You are an absolute life saver.

[xboxproscar]

I saw your other video you suggested and no matter what I do I can't figure out how you got -15. Can you please explain what you did to get that answer?

[robichaudd]

@xboxproscar I tried writing in the steps here but kept getting an error message. I'll send it to you by email instead.

[LordSunes]

@robichaudd Can you send me an e-mail to I'd didn't get 15.

[robichaudd]

@LordSunes Here's how to get D for the 3x3 Cramer's Rule video. The same process can be used for Dx, Dy, and Dz.

For D, expanding around the top row of 1,1,1 we get

1(-16-3)-1(4-1)+1(3-(-4))

1(-19)-1(3)+1(7)

-19-3+7

-15

Hope that helps :-)

[LordSunes]

@robichaudd Ah yes yes that's it, if you calculate slolt you dont do mistakes. Thanks for help :D

[arbindcoltene]

THANKS FOR YOUR HELP, UR REALY GOOG TEACHER.

[Rmoney10pk]

i love looking up explanations for things my teacher fails to teach

[Lingxor]

I love you.

[jg362104]

You didn't explain how you got -15, -30, 120, -15.

[robichaudd]

@jg362104 I had the D values done out ahead of time. For how to evaluate determinants check out my video on 'how to evaluate a 3x3 determinant' at my channel.

[rixiville]

@jg362104 dude simply take the determinants



[rixiville]

thanx bruh! it really helped me ...dis was so easy

[olheiser01]

@jg362104 you get a TI 89 calculator to do it for you.

[S33MeNoMoR3]

Thanks for your help, you're such a great HELPER!!!:DDDD

[jimmyreed112]

thankyou so much. just started an engineering course at university and the way ive been taught cramers rule was awful but this quick 5 minute video by you explains all :)

[omzz225]

THANK YOU :)

[benzbubblecat]

you sound like Leslie Winkle from The Big Bang Theory

[austindlisk]

Thank you!



[bordshat]

This is the way it should be taught it school. All my professors are so caught up with exact mathematical notation and the theory and the proving that they rarely get around to actually showing how to do the bloody thing. Thanks a lot!

[chocolatemilkyum]

actually easiest method on finding linear equations.

[jubinrockss]

cool....

[sharpenbullet3193]

thanks^2 !! you made my life so easy! :D

[lawrencewong100]

i got a question like this :

You are to solve the equations:

2x+9y=-37

11x-y=49

by Cramer's rule.

Write out the values of the 3 determinants required and the values of x and y.

How to get started?

[robichaudd]

@lawrencewong100 Try searching youtube for "2x2 linear system by cramer's rule." Basically, you'll want to use the same method as in this video, except you'll use only x=Dx/D and y=Dy/D, and each determinant will be a 2x2 determinant.

[Kiwi663]

Ehm...

I got 120 for y.

Do you have to multiply the det. in a certain order?

[anewbiginning]

thank you so much. i learned more with you than in my class.

[ctw005]

CRYSTAL CLEAR!!!!!!!!!!!! Systems of equations with three unknowns are so easy to solve now. What a life saver for my statics class and circuits class. Thank you so much!!!

[SLopez346]

how did she get -15,-30,120,-15?

someone help please. :))

[robichaudd]

@SLopez346 I had D values done out ahead of time. For how to evaluate determinants check out my video on 'how to evaluate a 3x3 determinant' at my channel.

[SLopez346]

@SLopez346 Thank you so much! I get the problem now :))

[oxymoron41]

didn't help at all thanks for wasting my time

[pmb092987]

Just as a heads up your solution does not work for this 3X3 system I'm sure you know that maybe you could post a like little tag in the video with a correction.

[robichaudd]

@pmb092987 The solution works - if you substitute (2,-8,1) back into each of the original equations of the system you get true statements.

[Darrknox]

I was looking over this video and going through the evaluation of the matrices myself using different methods, but I kept getting 150 for x instead of -30.  I tried it on the denominator determinant and the y determinant, and those were correct, just not x. I was wondering if the video was wrong, or if I messed up on it?

[robichaudd]

@Darrknox The Dx should come out to -30, not 150. Watch the signs when evaluating Dx. I think you might have had the wrong sign on the last term (which should come out to -90, not +90). Here's how Dx looks:

-5(-16-3)-35(4-3)+-18(1- -4) = -5(-19)-35(1)-18(5) = -30

[TehPenetrator]

This is why I hate Math. One person spends an hour to two hours lecturing you making no sense and then someone who knows what they're doing can show you in five minutes.

[THISISSPARTA827]

@TehPenetrator same here

[divvy1400yam600]

I assume these equations have one point in common ie are simultaneous.

What would happen if they weren't ?

[robichaudd]

@divvy1400yam600  If D=0 and Dx,y,z=0, then there are infinitely many solutions. If D=0 and at least one of Dx,y,z does not equal zero, there is no solution.

[RedDeadCornFed]

Thank you very much for this video!

[Bloodpipe07]

praise god for people like you, my ADHD kicks in while chillen in my Algebra 2 class, and i jusy completly zone out, thankyou so much

[cursedu]

You are an Angel sent by god to help me

thank you so much i wish you were my college professor.

God dam i love u

[wightnight81]

thank you. this was a great help i had no idea what my teacher was saying

[sk8rat18]

you sir, are truly a merit and a scholar.

[drgshnbs]

Thank you, this was very helpful

[austin123457]

i love you, tommorow i have a test, i was gone today and missed the review. I have to cover a TON of different things and i have to tell you. "If i knew you in real life, i would make the smoothest love to you"- Me

[Lilisama11]

Thank you!!! you helped me a lot!! ^.^

[ShaggyKiller]

I finally got it! it took me a couple times (checking odds in back of book) but I got it! Thank you, you saved my ass on Chapter 4 test tomorrow!!

[nabroyan]

Thank You very much ! It helps me a lot!

[iSUSHIXD]

love your video, it clarified a lot of steps for me & its so helpful! thanks :)

[1nglewattz1]

I like the short cut. But can I use this method other than 3x3?

[robichaudd]

@1nglewattz1 Yes, you can use it for any size linear system.

[Redhatboy008]

Very good video , has helped me much ! Thanks :P

[aljonloveiguibone]

this is easy... Thanks!!

[mysticwitch155]

Thank you so much! Your video has helped me much! :)

[sergeant07]

what is the method you use to get the -15 on D -30 on DX -120 ON dY AND -15 on DZ what did you do to get that?

[robichaudd]

@sergeant07 For how to evaluate the determinants check out my video on how to evaluate a 3x3 determinant at my channel.

[sergeant07]

@robichaudd  ok thank you :)

[AznBubblesz]

thank you so much!

[DarkVampiara]

Wow I love you so much! Thank you!! <3<3<3

[firealwaysworks]

Fantastic!!

[ThaChavez]

i love your handwriting

[carrotgrater1]

Thanks! very clear

[GlorifiedTruth]

Doing math with a Sharpie... now that's confidence.

[pumasfan2000]

thank u

[ahmeed350]

this video helps me alot

thank you very much



[lrakmatthewj]

Thank you so much! 

[1guerolito]

Your video was incredibly helpful! The way you explained Cramer's Rule was a whole lot better than the way my math teacher explained it. Thank you so much!! :)

[disornr]

God bless you !!!

[disornr]

You save my life!!! Thanks alot!!! Despite all the good explanation... What a beautiful voice!!

[fifabublz17]

gracias!!

[obesechicken13]

Thanks! I think it might be faster to do 3x3s by converting in to rref though? But when profs say this is on a test, I'll look it up again.

[SibirianBlue]

Thank you very much :)

[vinoth1804]

Excellent!!

[shinigamirenegade]

wow you teach much better then my math professor. thanks for your time for putting this video up really helpful thanx :-)

[Mans22323]

Thank you so MUCH , you saved me !!!

[freshskweezer]

nice video, thank you very much

know anything about network theory or circuits?

[robichaudd]

@freshskweezer No, it's been about 20 years since I did any circuit stuff. But keep looking in youtube, someone must have videos out there...

[alwaysazeldafan]

Would it be possible for you to make a video where you show Cramer's Rule used in finding critical points for a two variable system? your videos are very helpful, thank you

[robichaudd]

@alwaysazeldafan Sorry, but I don't have time to make new videos right now. Keep checking on youtube - there must be some videos out there somewhere on that topic.

[ProudSikhJatt]

Hi, got a question for ya, at the end of the video you calculated the D's section but how exactly did you count so fast and from where do you start to add/substract to reach that conclusion.

[robichaudd]

@ProudSikhJatt For how to evaluate the determinants check out my video on how to evaluate a 3x3 determinant at my channel.

[TrueReIigion]

ty for the vid it was helpful

[jk7070436]

THANK YOU SO MUCH! I have a math test tomorrow and you saved my ASS

[1Chriiz1]

great explanation!! THANK YOU!!

[I3ui2n]

thanks alot. I missed my class and this 5 min video was probably better than my 2 hour lecture

[KowanRKO]

so true LOL

[pop4ti]

@I3ui2n are you take this things in the university?

[TrueReligion823]

I LOVE YOU!!!!!

[omops3]

how did d=-15 Dx=-30  Dy=120 and Dz=-15

help me

[robichaudd]

For how to evaluate the determinants check out my video on how to evaluate a 3x3 determinant at my channel.

[JTS11d6]

Thanks so much, studying for finals!

[arsadogi]

Much love!!

[Lagunamof]

omg thank you soooooo much! i have my exam in like a few hours, and i finally get it!

[1bontenbon]

Thank you so much.thank you thank you thank you thank you. i can not thank you so much. you really did help me.thank you.=0 i finally understood why you set the columns like than.

[shocker664]

i love u . u gonna help me do my last midterm in lin !!!!

[Fruitzii]

Isn't gaussian elimination something to consider ?

[robichaudd]

Yes, that's works. The other method, expansion by minors, is shown in my video on "evaluate 3x3 determinant".

[godleeone]

all you did was setup the easiest part of the problem, and wrote out the answers.... Weak.

[whisperpro]

you five minute video taught me more then a half hour math lecture, thank you.

[GretzkyTheWonderDog]

holy sweet jesus,

you have just saved me from failing my alg 2 class

[salamence47]

I taught it is so hard...

but because of you, you made it so EASy!!

:P

thanks!!!

[CxRol]

Thank you so much!!!!!

You made it so easy!!

[freeocean09]

robichaudd, u helped me go through this chapter thanks

[davidjosephraymundo]

4:15 - 4 :23

Where did u get it?

[robichaudd]

For how to evaluate the determinants check out my video on how to evaluate a 3x3 determinant at my channel.

[PearlsphereBiophilia]

Thanks so much! you saved my day! My lecturer gave a surprise quiz today. I referred to your video and got the answer! hoorah!

[jboxerman08]

i have a problem i have to do and when i use cramer's rule, i get 0 for the fundamental determinant D... does that mean cramer's rule doesn't work and that I have to do it some other way?

[robichaudd]

It still works, it just means you have either a no solution system or infinitely many solutions system, depending on whether your other determinants equal zero.

[jboxerman08]

alright, thanks alot! that video was a really clear explanation of cramer's rule btw!

[reflexesir]

This video is ABSOLUTELY perfect. Thank you so much!!!! I did not understand it in my book, but this made PERFECT sense. Thanks a lot!

[ivydagamer4life]

i got it, but there's only 1 question i wanna ask and that is on 4:17-4:23 .. on how have u answered that. Now i must figure it out.

[matchxCx]

Thanks you so much !

[ndog33]

Just one thing robichaudd u read the numbers in a matrix from left to right like a book.

[naix319]

you have a sexy voice

[reallybored03]

This explanation was clear as day!

[hpceo01]

Thank you sooo much. You have saved me alot of time and energy. I have been paying for tutors and struggling and I have a learned faster and more in depth with you for free on youtube. Please keep doing what you are doing. As a student I truly thank you:)

[skoushik333]

How did you find the value of the determinant so fast? o_O

[robichaudd]

I probably had them done out ahead of time. For how to evaluate the determinants check out my video on how to evaluate a 3x3 determinant.

[democraluv]

Does this work for 2 by 2 and 4 by 4?

[robichaudd]

yes

[matsafuan]

Thanks a lot!  ^_^

[kpkkpk]

should have showed how to take a 2x2 matrix out of the 3x3 to solve for the determinant.

Would have made it a lot easier. :)

[feryolfels]

so much thanks!

[dlewinski]

THANK YOU SOOO MUCH!!!

im studying in a foreign country, with no text book and the professor is always impossible to find. ive got an exam tomorow on this and I FINALLY GET IT!!! thank you thank you thank you thank you! haha

[DiegoBloody]

OMG ... thanks ^^

Now I understand xD

Cheers from Peru (:

[kberg900]

Very helpful. Thank you!

[brilliantfranz]

excelent video, very heplful and clear

cheers from Venezuela

[9911679695]

superb way to explain , Thanks!!!!!!!!11

[sloppyjoes7]

Wait... I thought you were patrickJMT.

[zqkun]

Many thanks ! I got it:)

[naciondebastardos]

ok chido! gracias por tu tiempo