Solving Simultaneous Equations by Elimination Example 1

[spencerseth]

I'M READY FOR THE TEST! COME AT ME BRO!

[06shiningstar]

Thank you so much!!

[jimmygirlxx]

How would you work out an equation if there was an 'x' out the start? eg: x+2y=12?

[peaceandlovein69]

sounds kinda like the headteacher from inbertweeners

[Brickcellent]

@peaceandlovein69 Gilbert, yeah.

[ihavefourpaws]

WHY DOESN'T MY TEACHER EXPLAIN IT LIKE THIS!!!!!!!!

[JoshuaCecilJohn]

My maths teacher explains it exactly how you do. Somehow, I seem to get it better from you.

[ProNinja72]

thanks for the help. i was really confused on how to work out Simultaneous Equations because my maths teacher explained it the complicated way but this method is much simpler.

[sladkoCCCC]

where did 180 come from

[Brickcellent]

@sladkoCCCC 36 X 4

[sladkoCCCC]

@Brickcellent aha thanks

[TheSecret20111]

@sladkoCCCC Firstly it was actually 108 not 180. Secondly it is just 36 multiplied by 3. He got this after multiplying the whole of equation 2 by 3, and if you multiply the equation you also have to multiply the answer.

[sladkoCCCC]

why does y dissapear when x is 25 21 +4 =25 then y dissapears why ?

is it just here or everywhere

[aussienerds]

I'm still SO confused! Why does a software development course in university insist on me completing maths methods. I hate it!

[sladkoCCCC]

WHY IS THIS SO FUCKING HARD,WHEN AM I EVEN GONNA NEED THIS IN LIFE ????????

[spikeyredcactus]

@sladkoCCCC perhaps if you want to go to university and actually know how things work? look around you. Everything uses maths idiot. Perphaps if your aspirations in life are to work in the local pound shop then no, your not going to need this in life. In which case you might aswell drop out now.

[sladkoCCCC]

@spikeyredcactus tell me who uses this except for scientists

mechanics dont car salesman dont i could go on and on and on yes its important but come on this dont happen in an everyday situation

[spikeyredcactus]

@sladkoCCCC hmmm, spose, im doing a bachelors in mech eng, but its still important to get a basic understanding of this stuff at school. I used to think the same as you when i was at school. Trust me, its not pointless, even if you cant see it now.

[sladkoCCCC]

@spikeyredcactus yeah i guess your right

[emporerbond]

absolutely brill, my homework is to create a video doing this so thanks a bunch! :-D

[Zalorah]

This was fantastic, thanks heaps.

[alexcravenator]

been studying these equations for 4 years AND THANKS TO YOU I NOW GET IT!

[danae1996able]

Better than how my maths teacher explains it...... =)

[emporerbond]

i hear ya

[Adilshit]

my math teacher is the worst, this guy saves me and explained it to me easily

[LuBabaChica]

i'm confused too.. why 3?

[Adilshit]

@LuBabaChica so that number 2 will have the same y as number 1, or else it will be impossible to solve without two same y's

[MultiClinton1234]

@LuBabaChica the y is empty and the other one is not.so you have to look for a number that will make the y columns the same.and 3 was the possible number.

[HelloKittyMADx]

What if x and y are the same in the equation what do you do then??

[HelloKittyMADx]

THANK YOU SOOOO MUCH I WAS PANICKING ABOU TTHIS SOOOOO MUCH BUT NOW IT ALL GOOD!!

[wspunkrocker]

Thank You :D

[Themesticks]

problem is, im doing GCSE and ive got squares?!?!?!, anyone fancy a walk though of;

2x + y = 6

x^2 + y^2 = 20

[MrJakey121]

thanks you helped a lot :)

[Nightkidz884]

THANKS!!!! you save me from my math teacher

[TheYungbrEz]

thanks, it really help cuz i have a test tomz =P

[gadgetzcentral]

thanks, helped alot!

[syedaxx4]

LOOOL:Lx im confused! is it 3 or 2?:/

[Usernameshouldgohere]

but why do you multiply everything in equation by 3?

[MechanicallyGreasy]

@Usernameshouldgohere you have to get the y's or the x's at the start to cancel off each other so to do this you have to find what multiplies by what for example :

4x+8y = 20 &

5x-2y = 30 you will then have to multiply the second line so that it will equal -8y

(4) 20x - 8y = 120. hope that helps =D

[wilson8225]

this helped alot thanks man :)

[RNClarke76]

how did he get 3y = -3?

[LIFE478]

@RNClarke76 17 minus 20

[HaniiBabeii]

@RNClarke76 Because when he took 20 over to the other side, it become 17 minus 20 which equals to -3

[Wacklewis]

@Darkvampire376428 5 x 4 = 20

[Darkvampire376428]

Where did the 20 come from???

[DAJOK3R100]

how did he get 3y = -3?

[umarnobbee]

@SingingEgg if you have sense you'll know that's wrong 20 - 17 equals 3! :D

[maxipriest96]

Thanks a lot.

[TeHTRUPH33R]

I STILL DUNz Get

[SleekDan97]

This helped so much! Thanks for posting!!!

[kingrobinho77]

why do you elimate y and not x...would help if quick reply exam tommorow

[kaaaaazzzz]

@kingrobinho77 because x comes before y  ;) haha

[saba43va]

im fucked tomorrow

[ROBxSKATE]

i thought 4 times 7 was 28 not 21

[lass961]

How did he get Y=-1? Really need to know please anyone....

[saba43va]

ok, im totally fucked

[juiceboxwars]

Thankyou! Maths exam Wednesday, you saved me!

[Mrsuperswifty619]

@juiceboxwars LOL same i got an exam on the 9th november aswell

[juiceboxwars]

@Mrsuperswifty619 Good luck! :)

[Mrsuperswifty619]

@Mrsuperswifty619 LOOL i swear down a simultanieous question came up in the exam and i DESTROYED it. :D

[Vintelyz]

@Mrsuperswifty619 the 9th november one?,

[Gergyboy101]

Why do you multiply it by 3?

[magill678]

how come sometimes there are two lots of solutions for x and y?

[17xDillz1997]

THANK GOD FOR THIS,,I SLACKED OFF THE WORK AND WENT TO FACEBOOK

[KatoDM]

how is 3y = -3

[000wowtube000]

@KatoDM 20 + 3y = 17 So you solve for y Right, so you take 20 to the other side so it will change the sign from positive to negative so 3y= 17-20 so ((3y= -3)) Continue solving for y so you cancel the 3 in order to get the value of y by dividing -3 over 3 which is equals to -1 so y = -1

[TheMoo1231]

@KatoDM 3 times -1 is -3 xd

[empireofthekopTV]

@KatoDM 17 - 20.

[kingrobinho77]

@KatoDM lool float and ping 17-20=-3 :)

[Maffewvids]

@KatoDM y=-1

[YvonneTominez]

@KatoDM,

Because you must bring the 20 over to the other side of the equal sign which becomes 3y=17-20, then you must bring the 3 over to the other side of the equal sign which becomes y=-3 divide by 3 which gives you y=-1

[SingingEgg]

@KatoDM Because 20 - 17 = -3

:)

[LetMeBeUrSupernova]

what does he mean by the signs are different?

[FreeKicksPFC]

ok like if you some reason not a whole year from last years 11 and have a maths exam tuesday

[aligmac7]

y=x+3

y=7x

anyone?



[erinl400]

I FINALLY UNDERSTAND. I LOVE YOU

[poyanator]

what if you have THREE unknowns and THREE different equations??

[wolvez2]

Haha i don't really understand your question, but he multiplied the 2nd equasion by 3 because then both equasions would have 3y. So then at least one thing would be matching. Then he can go on and solve the two equasions once something is matching. You do this with all other simultaneous equasions... It doesnt matter what youre trying to make both equasions have in common, but thats how he knows what to multiply them by.

[TheBurningHateWithin]

Finally, it makes sense.

[cherry2047ful]

i really dont get this where did he get -3 from someone plz

[wolvez2]

@cherry2047ful He was moving the 20 to the other side of the equasion, so he took 20 from 17 which gives you -3.

[cherry2047ful]

@wolvez2 do u wen he labels da equation 1 nd 2 hw does he kw wat 2 times equation 1 nd 2 by. wen i was watching example 2 hes timed equation (1) by 5 and equation (2) by 3 i get dat cuz he got da 5 frm equation 2 nd he got da 3 frm equation 1 but then in some ex he doent do dat method he gets other NO nd times it by equation 1 and 2 that i dn't get i thought dat u always do it the way he did in ex 2 eg 4x+6y=18 nd 11x-8y=-73 so (1)x11 nd (2)x4. in dis same ex he used (1)x4 nd (2)x3 y.(plz help)

[JackColquhoun]

Thanks for the tutorial my friend

[Jomac37]

would this work for an irish higher level student? or do you not know the sylabys? p.s im 14!

[Morethanicouldhandel]

Bloody simaltaneous equations how do they work

[stevenlpfc]

Hi, what do you do when you get 2 constant variables?(if thats what they are called)

I have 4y-x=4 & 2y+3x=2. By multiplying (1) by 2 and (2) by 4 i get 8y-2x=8 and 8y+12x=8. By then minusing (3) from (4) i get 10x=0. Where have i gone wrong as 0/10 cannot possibly be the answer. Thanks

[RUBZ241]

thanx this helped me sooo much

[ryandarrenpocock]

i love you for this

[crazywwefan47]

Thanks a lot friend

[76mrlonely]

this helped...thank you so much.

[Sillyguy610]

I am too slow with math, that's why i am not understanding when my teachers explain it because they were so fast. but you're good in explaining :)

[SilebPRS]

Thanks a lot, you're a great at explaining this.. You just (re-)taught me 2 weeks worth of this in 2 minutes 51 seconds.

[MsAndrew1122]

why do we multiply (2) by 3

i don't really understand were three come from please can someone explain me?

[Danisfail]

@MsAndrew1122

So that the y's are equal

[yesudeep]

@MsAndrew1122 You multiply equation 2 by 3 to get the -y to become a -3y. So when you add both the equations the +3y and the -3y will cancel out and you will have one equation with only x in it. That's easy to solve.

[000wowtube000]

@MsAndrew1122 We multiply 2 by 3 in order to make -y to -3y so then we can Cancel the y and solve to get the value of x

[patricklove1000]

@MsAndrew1122 you see in the two equations that there is 3y in line one and only 1y in line two................you multiply line two by 3 so that they would cancel off each other

[empireofthekopTV]

@MsAndrew1122 so that y becomes 3y on the second equation. then you can cancel them out.

[YvonneTominez]

@MsAndrew1122 ,

We multiply equation (2) by 3 so the Y value is both equations are the same so we can eliminate the Y value when we add by equations together.

[itsamariokart]

@MsAndrew1122 because we want all the Y's to be equal. So if you multiply Y by 3 you will make them both 3Y.

[123321peteyg]

@MsAndrew1122 minus the 20 from 17 

[shaeann123456789087]

@MsAndrew1122 HE DESNT MULTPLY (2) BY THREE... (2) MEAN EQUATION TWO..SO U MULTPLY EVERYTHING FROM EQUATION 2 BY THREE.

[Nitromethanification]

@shaeann123456789087 yeah.....but why 3?????

[Minaj53]

@Nitromethanification equation 2 (y) doesn't have a # so i guess he was trying to make to equations 1 and 2 (y) and use 3 same as equation 1

[bazzaboy45]

@MsAndrew1122 thats how many y there are

[AyrtonKelly]

Still don't get it; God I hate maths like WHY do we have to learn these!?!

[TheMrAbdulhaleel]

thanks.... i did my exams 9 years ago. But forgot all about this. got it back ;)

[eatmeaters]

Math exam in a 3 hours, wish me luck

[EvilBowl0fCereal]

you know there is an aptitude test about methods of how people mostly prefer to learn. I took it in school yesterday and it turned out im one of those ppl who prefer watching something and lerning than reading or listening. Maybe thats y u all coudnlt do it without this vid

[EvilBowl0fCereal]

thank you sooooooooooooooooo much your explanation made it easy

[Bugginton1]

THAT WAS BRILLIANT! Thanks a lot, that's helped me out of a sticky spot with my college prep work :D

[arghydoodles]

My teacher used to say that you can think of the addition sign as a male and the subtract sign as a female.

And thus, if you have a female and a male, you put them together (add). If you have a male and a male or a female and a female, YOU BE HOMOPHOBIC AND TAKE THEM AWAY YEAH.

[purpleplums100]

at 1:55 why is 3y = to minus 3???

[mafiamaster100]

@purpleplums100 because you are taking 17 over the equals sign which turns it to -17 so +20 and -17 will become -3 as a plus and a minus will become a minus

[BabyAbood123]

@purpleplums100 cause you want to make 3y on its own so what you do is you bring 20 on the other side which will be minus and -20+17= -3 :))

[MattBrice1]

i learnt more from this 3 min video than 2 months of doing this at school

thx :)

[MrNeoHerman]

why (2) x 3 ? where the 3 come from ?

[InTheoryGuild]

@MrNeoHerman He's multiplying the whole (2) equation by 3 so that you can get the same amount of 'y' in each equation. The 3 is just a thought up number, you could multiply (2) by 6 and multiply (1) by 2 if that helps you understand.

[imasingaporefreak]

My GCE N level exam is coming and i still don't understand this topic . atlast , after watching this , i can roughly understand the topic .

[dannyk01]

OMFG, thank you so much, you did the job of my teacher in 1 min 30 seconds :O He tried teaching this in about 40 min and I still didn't get it. THANK YOU THANK YOU

[halfemoshit]

DANG, THIS HELPED ME. MY MATH TEST IS TMR AND THIS HELPED ME SO MUCH.

[imagination774]

Man thanks >.> im only in primary school but its gona be useful to me,my teacher said

[ItSaGoodGoOdDay]

woah *_*

[blackhappiness2]

I love this....staring at my book wasn't helping me absorb anything!!

[Gbiney]

Thank you so much, i have tried everything even GCSE bitesize and they still made it confusing, SO GLAD THERE IS YOUTUBE

[ilookaturvid]

i have my mqths GCSE exam tomoz

[leepaulalexander]

thanks you made it so easy, test in 3 days and this helped allot

^^

[Theyutubevids]

Test on monday... this helps!

[nooboftheforest]

Thank you, your videos will be very useful for revision.

[pg6t55]

got a GCSE year 10 mock , determines if i will stay in higher tier , ive been slacking and this helped alot ha ha , myteacher doesnt explain properly coz of accent :P

[bobetninja]

i knew how to do it but i just didnt no how to check it.now i no so thnx

[CtrlAltxMasterx]

why does he times by 3!! someone help, why not like 5 or 8?

[ElderScrollsGamer]

@CtrlAltxMasterx He times the second equation by 3 because he wants to make the y's the same in both equations. By leaving the first equation as it is, and by timesing the second by 3, both equations then have a value of '3y'. This is the lowest common multiple of 1 and 3, and therefore that's why its used.

[335crowy]

This has helped me 10x more than my maths teacher ever has.

[ostime14]

IM FUCKED FOR OUR EXAM LATER!!!

[padswolf]

i have no need for school anymore ._.

[jekquirock]

3y=-3 because he subtracted 20 from both sides to get the 3y on it's own. He subtracted 20 from 17 to get -3. So 20+3y=17 goes to 3y=-3

[1111Owen1111]

Why does 3y= -3???

[lleewwiisss]

@1111Owen1111 Because he had to balance 20+3y=17

And to do that he had to put the 20 over on the other side, which means it turns into a negative, so 3y = 17-20

So therefore 3y=-3

Understand?

[Beccathecoolie]

If i get this right in my gcse exam tomorrow, it'll be a bloody miracle, but this made it almost possible

[nazmiyax]

Thumbs up if your dreading for the maths exam tomorrow :/

[Shesfabolousss]

1;53, how did he get 3y=-3 ?

[321emilyemilyemily]

12 people still couldn't do it !!!



[TheLizamoon]

@MrTwat444 Because you need to get Equation 2 similar to Equation 3. By multiplying Equation 2 by 3 you get 21x-3y. It's kinda similar to Equation 1 which is 4x+3y. The Y's are the same. Later on, you add and subtract and do all that shizzle to get the answer. You get? I don't get it myself but I'm trying to help. I don't know why though. I should be revising. O_O

[kidru23]

there are some helpful people in this world and you are one of them

[metodeeworld]

wow this is great thankss!

[Ghoosted]

LOLLL. Last minute revision.com!

[McHuZii]

LOL most of us have our GCSE maths exam tomorrow Thanks for the help!!

[Tidulz00]

Thanks for clearing that up for me XP

[sososoSOPHIExo]

I LOVE YOU! MY MATHS TERMINAL PAPER IS TOMORROW

[SellyB90]

I LOVE YOU

[BIGBalls136]

Thank you so much ! If anyone has maths watch throw it in the bin this is so much clearer !

[mrtictac94]

Ta mate, dreading simultaneous equations much less for my GCSE tomorrow

[VariedLyrics]

Brilliant, I kinda knew it, but I wanted to make sure. Cheers man, aiming for my B grade tomorrow :)

[fly144bin944]

makes no frigin sense!

[888punjabi]

thanx alot. u taught me sumthing in 1 day in which my teacher cudnt teach me in 1 whole year.

[Bennzy100]

why do you mulitply by 3 at the beginning?? :P this is so confusing for me :P

[iMarinaH]

@Bennzy100 To equal the amount of y's on equation 1, therefore cancelling them out - it is quite confusing at first! Once you get your head around it, it's easy really! :)

[Bennzy100]

@iMarinaH yhhh i think im doing the Linear paper so this is a different method

[iMarinaH]

@Bennzy100 Yeah, you do. This video is about simultaneous equations... you need to look up LINEAR equations. :)

[Bennzy100]

@iMarinaH Ohh okaay kool Thank you :D

[MegaMagicStars]

@Bennzy100 you want to get 3y in the second equation so that you can take out both of the 3y's. basically when you first get the equation, your main goal is to get one of the coefficients ( numbers before the letters x/y) the same. here, the first row has 3y and the second is only y. so we can times the bottom row by 3 to change this y to 3y, you could hav done picked another number to get the two x's the same, but in this example, it was easier to make y the same :)

[Bennzy100]

@MegaMagicStars Yeaaah aww thankyouuu but do you do this in the Linear paper? because theres another video that says Linear on it and its a different method :P :) Thank you againn :D

[MegaMagicStars]

@Bennzy100 sorry, but i really dont know anything about 'linear' if the topic is simultaneous equations, im guessing its just a different method to get the same answer. sorry i dont know, the only thing i know is that i use this method when i get given a simultaneaous equation :P and you're welcome :)