Make sure you only do this with LINEAR systems of equations. AND check out my MATH TRICKS playlist! kzfaq.info/get/bejne/gdldqtqK1bmWYI0.html

Algebra, please stop asking us to find your X, she is never coming back and don’t ask Y

I took the risk on doing this technique in our Calculus exam, and it saved me a lot of time. I practiced your technique, sir. Afterwards, I used the same old process (Elimination-Subtitution) and yeah, I got the same answer.

I really hate math because I feel like my future depends on it and if I dont pass I won't graduate it puts me a lot of pressure.

During the pandemic I've decided to get into Math as a hobby. I've always wanted to just never had the time. This is an awesome trick. Thanks for sharing. Anybody have any suggestions. I'm building up to Physics.

In India, we are taught this like a formula. This method is called the cross-multiplication method. The formula goes like this. For the standard form of system of equations a1x + b1y + c1 = 0 and a2x + b2y + c2 = 0, x/b1c2-b2c1 = y/c1a2-c2a1 = 1/a1b2-a2b1 This method is not exact to the method you said, but it is indeed similar...

did he just solve an equation, backwards? wow

this is why i miss school i need to learn and virtial learning isnt helping me with math

Does he ever forget there's glass in front of him and he accidentally bumps his head on it

This is called Cross multiplication method and very helpful when coefficients are small enough to multiply easily

This guy...right here...is an absolute legend.Thanks alot for showing this method,I'll make sure I forward this to my friends and teachers!

This seems like more rules to memorize without understanding why it works. I dont think its worth memorizing this for such a small use case. I would rather do a tiny bit more work and be more confident in my answer. But cool trick nevertheless.

I figured this out completely on my own when I was 18. I was going through my College Algebra book and was obsessed with finding shortcuts to solve things faster.

Oh my gosh, thank you so so much. I am from Singapore and I’m secondary 2 or grade 8, the whole textbook was algebra, and you helped me so much, oh my gosh I can’t thank you enough!

im crying you are so amazing, ever since grade 7 i have had terrible teachers so i struggled with basics and now i am in gr 11 and i have came so far with you videos .

This is amazing how I learnt how to solve an equation In less than 1 min

I just realized this guy is doing the equations backwards. Major respect for this guy he is the maths teacher we needed.

I thought about falling face forward in my notebook but I was like “Really you know you can do way better than just give up”, found your video!

Wow I really enjoyed this video. I actually just finished linear algebra and solving systems of equations was a lot easier in matrix form. I wish I would have known about this back when I took algebra in high school. Love your videos. Keep up the good work.

For anyone curious: You can have this written down as Ax + By = C, and also Dx + Ey = F as the second equation. If you isolate y in the first equation, you’ll end up with this equation: y = (C - Ax)/B Now, if you plug that value of y in the second equation, you take these steps: Dx + E[(C - Ax)/B] = F Dx + (EC - EAx)/B = F (DBx + EC - EAx)/B = F DBx - EAx + EC = FB (DB - EA)x + EC = FB (DB - EA)x = FB - EC x = (FB - EC)/(DB - EA) x = (BF - EC)/(DB - AE) And that’s exactly what’s done here

Thank you so much Brian. Found this video last minute before my tests in Maths. It is very useful and I definetely subscribed. Thank you so much, Really appreciate it.

I was taught about it since I was in primary (elementary) school. But I never know its name until I got into university where I took up Math as my major. It felt incredible at that point to finally understand the mechanism behind this formula. I will not disclose its name but let your curiosity run its course if you so wish

U probably won't see this but this helped me soo much I've been really struggling on algebra because most things my teacher says make no sense so thank u

3:00 Lol I remember my buddy Cramer in Linear Algebra. What a cool use of determinants

To tell this more simply this is the x/() =-y/() =1/() trick In those brackets the coefficients of other than the variable you're writing it below.

Thanks, It really helped me a lot . Teaching + Explanation + Opposite writing = 💯 out of 💯 👍👍👍👍

Replying to comments a year after, instant subscribe.

Having already done solving simultaneous equations using matrices - literally, explicitly using the matrices - I immediately went “so he’s doing the matrix stuff, just implicitly” before you even said. Still a cool trick to know.

watching it on quarantine at may 2020, subscribed. you're my life saver. i hope i could do this in 7th grade

I love your videos. Could you please share some tips on how to make Real Analysis a bit easier?

Basic idea of algebra, but very essential ones. Learnt a lot from this video. The way you present the lesson make it looked so easy. The explanation also very smooth and easy to follow. so happy find this video. Thank you very much.

That's pretty cool. I never thought to cross multiply like that.

We were taught this in elementary school, it's called CROSS MULTIPLICATION METHOD. We got 4 methods:- 1. Substitution method where we find the value of one variable and substitute it in the other equation. 2. Elimination method where we try to eliminate one of the variables by substracting, dividing, adding, or multiplying the equation. (My favorite) 3. Shifting method where we find the value of one particular variable (say x) from both the equation and then equate it with each other and solve for it. 4. Cross Multiplication method The thing is that you just showed it directly but we had to do certain steps before that. Nice Video BTW

So I'm not great at math but I remember when I was little my dad taught me all about matrices and determinants for no reason and so this trick made a little more sense when you told it.

This is called the cross multiplication method. It's super common in India. There's a whole exercise based on this method in 10th grade textbook

I think using the original order of calculating what would be the "determinate"( instead of reversing the order) is yet easier in terms of visualizing the simple cross-multiplication involved. In any case, just another tool I'll put in my tutoring toolbox. One of my favorites is for fiddling the turning points (relative max and min) for a cubic function. We all know the quadratic formula, well the formula for the X-values of the turning points of the cubic AX^3+BX^2+CX+D is practically the same. Instead of B^2-4AC inside the root, it's B^2-3AC and instead of dividing by2A, divide by 3A. If "A' is positive, the smaller X belongs to the relative MAXIMUM and the larger X belongs to the relative MINIMUM. If "A" is negative, vice versa. This formula gives EXACT answers instead of the approximations found by graphing on a graphing calculator. It's pretty cool. Cheers. And LOVE your channel!

this is awesome how you do it so fast! but i just started so I didn't understand much lol btw i subscribed

I mean I guess it could be faster, but if you're fast at solving with elimination, it could work better. Either way, it's a neat trick to know and I will use it sometimes

I guess that's a kind of cross multiplication method that we as well as our teachers used to skip in our schools:)

I love this man soooooooo much right now. This is so freaking SIMPLE!!! How many videos have I watched and NONE of them put it so simply. This will save me a lot of time on my math homework.

Question. How do you know which ones to myltiply first, and which ones to minus, like which equation to put at top

this is SUPER MINDBLOWING AND IM IN GRADE 5 THANK YOU BRIAN THANK YOU

I love using Gaussian elimination and I kept thinking of it as a solution for all the systems until the end of the video 😂

When I found out about cramers method and also inverting matrices through cofactors I felt like I found something I was missing for so long in my other classes. I also think it's interesting that if you divide by 0, there's either no solution or infinitely many solutions through the invertible matrix theorem.

My eoc is tomorrow and I think I'm gonna fail, I dont get why they gave us testing this year with covid 😭

Seems more confusing than (1) multiply top equation by 2, giving 2x+4y=22, (2) subtract eq 2 from eq 1, so 2x+4y-(2x+y)=22-10. 2x cancels out, so 3y=12, y=4.

Seriously, I didn't understand anything Guess I forgot everything from highschool Is this for beginners? BC I think I should start worrying about myself lol Do u have lessons for complete beginners on Algebra

You make it easier, Thanks for your videos 💕💖

That's amazing bruh. Thank you so much for info !! :D

Do y'all realize he has to write opposite so we can see it lol

That trick is the short version of Cramer's formula. Neat!

Thank you King! Respect from Indonesia 👍

i'am loving this trick!!!! shouldn't learn this sooner!!

Thanks for all the tricks :D. I love all your tricks :)

Nah man thank you so so so much, I spent 5 hours trying to learn how to solve system of equations using matrices and I learned right away how to solve it right after watching your vid.

As a math teacher for 42 years I must say WOW! This is such a neat method that should be added to the other ways a system of 2 linear equations can be solved. What is needed is an appropriate name for this method. How about the XXX method or Crossing the System or ______. Cheers

Your awesome. I am a newbie. Does this method work all the time? Second question, do you have more tricks? Thank you

Hi Brian your video are very useful I have subscribed thanks for all the tip and tricks it really helped me in me exams

actually, in India cramers rule is taught to us in 10th grade, so as soon as you begin multiplying that way i understood you were finding D, Dx and Dy. Awesome trick tho

Somebody give this man a medal

Wow thanks i love this im now perfect at algebra thank you sir!

Pls include the 3 equations trick i love learn that pls

this video was such a big help! thank you so much!!

My problem is that I just forget how to do stuff like this, it’s fine in other classes but only in math I tend to forget formulas or how to solve. Do you have any tricks for that? Thanks

Not me watching this before a test:

This had really help me

This helped me alot, Thank you so much!

Amazing first time exposure with this guy

Thanks 😘 bro...It was really needed by me....

He is pro at this :O

My first thoughts were matrices and determinants but then you gave the answer yourself!!

Thanks bro tomorrow is my algebra exam it helps me lot it make me understand easily now i m going to practice it

It is just the cross multiplication method of solving equation...taught in class 8-9-10th in India.....he just tell it in a simplified way.....but still great video

This is actually something we are taught along with elimination and substitution, generally referred to as cross multiplication. I never really used this though, because there's a lot of room for error, like you wrote the coefficient of x instead of y, etc. Still, a good method to know 😇

Hi, Would you mind if I ask you? Is this trick available to all given problems in algebra? I just wanted to know. Thank you.

For those of you who could not get it, this is cross multiplication method for solving for simultaneous linear equations

You solved for X in under 30 sec. Granted, the writing and demonstration took up the bulk of the time, not the thinking part of the math. I appreciate a clever math trick as much as the next mathematician, but I solved for X myself using standard substitution method and it seemed easier and took less time for me. Maybe this is due to me being used to doing it that way for over 40 years, but substitution has the additional benefit of understanding the values. The alleged time saver is fun but I believe kids should know why the values are what they are.

Wow!!!

I swear to god this literally took his maths gcses with the most abnormal techniques and tricks whilst writing backwards 😂

do you have to arrange the equations so the x's and y's are stacked with the numbers after the equals sign?

WTH! What did I just see! Algebra made easy....NO WAY!!!!

When you realize you will get 1/4 marks for this instead of 4 or 3 points

Having trouble with rational expressions. Can you do a vid on one please thanks

Magical

Flawless

This method is taught in schools in India Infact it is even in the maths book and compulsory to learn < we call it the cross multiplication method here

That is some quick maths, that big shack would be proud of

I'm going to stalk this guy down if his algebra trick doesn't work on my test tomorrow

This was a great video really appreciate the technique! What about systems of equations that have no solution? Such as: -4x + 8y = 1 and 3x - 6y = 2 I tried using this rule for these equations but when plugging them back into the original equation they do not work. When using the elimination method the answer ends up being a contradiction with no solution. Would Kramer's rule still be relevant for these types of problems?

This trick is awesome!

This is perfect thank you so much but I was just wondering if this worked on all algebra

Does this have something to do with how they're solved with matrices? And the steps you do somehow calculates the inverse?

❤️

I love algebra * - *

At the end it is just the formula for the inverse of a 2 by 2 matrix. I used to solve system this way to be free of the value of the right side. A^(-1) = 1/det(A) [[d,-b],[-c,a]]

I was thinking about how similar this is to matrices and determinants when you were solving it. Guess I was right

I suck at math why did I sign up for algebra damn my over achiever self (I’m in 8th grade) * * * •update: I’m actually doing pretty good it’s easy just kind of useless and takes way to long to solve a one question•

I've seen this before, but I wouldn't call it a "trick." I mean, I could be wrong, but I think it's just Cramer's Rule. You're just writing less down, which saves a few seconds.

Thank you wery mach !!!!! This wideo really saved my time !

Thanks for the great help