You are Here: Home >< Maths

# Simultaneous equations

Announcements Posted on
Why bother with a post grad course - waste of time? 17-10-2016
1. (Original post by RDKGames)
12x + 8y = 88 ... (1)
10x + 8y = 46 ... (2)

Subtract (2) from (1) on both sides.

and you can solve that.
would it be x = 21??
2. (Original post by Jack_Tomlin)
would it be x = 21??
Yep. Now substitute that back into one of the two equations and you can find what y is.
3. (Original post by RDKGames)
Yep. Now substitute that back into one of the two equations and you can find what y is.
Ok so like this?

126 + 2y = 22
105 + 4y = 23
4. (Original post by Jack_Tomlin)
Ok so like this?

126 + 2y = 22
105 + 4y = 23
No.

You found that x=21. Now choose whichever equation you want to substitute it into, it doesn't matter, you would get the same answer from either.

Let's choose the second one for instance:
Since we know x=21 we can replace x with 21

and you can solve from there.
5. (Original post by RDKGames)
No.

You found that x=21. Now choose whichever equation you want to substitute it into, it doesn't matter, you would get the same answer from either.

Let's choose the second one for instance:
Since we know x=21 we can replace x with 21

and you can solve from there.
So we always sub into the equations where we made the coefficients the same not the first lot we are given?
6. (Original post by Jack_Tomlin)
So we always sub into the equations where we made the coefficients the same not the first lot we are given?
You can sub into either, the ones you make up are only multiples of the original ones, they don't affect the final answer after you simplify everything.
7. (Original post by RDKGames)
I feel the same way lol, but would't want to be rude or anything. I wonder what year OP is in.
No idea but I expect 7 or 8 as these are extremely basic simult eqns. Don't know why this thread has so many posts lol

Posted from TSR Mobile
8. (Original post by Jack_Tomlin)
So we always sub into the equations where we made the coefficients the same not the first lot we are given?
It doesn't matter as long as you replace one variable so you only get one variable left in the equation. When you made the coefficients the same, you only multiplied both sides by a scale factor so the equations are basically still the same.
9. (Original post by 98matt)
this thread is infuriating. Add them together, it's not hard. Watch some tutorial video if you're unsure. x=2 y = -0.5 is the solution

Posted from TSR Mobile
Sorry but I'm sitting the new GCSE maths exam next year foundation tier and a alot of the higher tier topics are moving to foundation as well.
10. (Original post by Jack_Tomlin)
Sorry but I'm sitting the new GCSE maths exam next year foundation tier and a alot of the higher tier topics are moving to foundation as well.
I don't mean to sound rude but it's clear that you're not sure what you're doing at all. I would go on YouTube and watch a few videos on simultaneous equations and watch how other people solve the questions and then try some yourself from a textbook.
11. (Original post by NeverLucky)
I don't mean to sound rude but it's clear that you're not sure what you're doing at all. I would go on YouTube and watch a few videos on simultaneous equations and watch how other people solve the questions and then try some yourself from a textbook.
Agreed. He just seems as if he was thrown some simultaneous equations without any background knowledge on them. :/

(Original post by Jack_Tomlin)
Sorry but I'm sitting the new GCSE maths exam next year foundation tier and a alot of the higher tier topics are moving to foundation as well.
OP, you can watch these videos made by my teacher and I'm sure they will prove extremely helpful. https://www.youtube.com/watch?v=_hsUrfF9rOs

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: July 31, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

### How does exam reform affect you?

From GCSE to A level, it's all changing

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read here first

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams