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# GCSE simultaneous equation help please watch

1. (Original post by Blaze3211)
Why did you make the top equation negative?
2. (Original post by Green22)
I thought too it was something to do with 130. Anyway 130/26=?
Wait, so is your problem just with working out the value of 130/26? Do you understand how to get to y=130/26?

3. Hello

I'm an A2 Mathematician and Year 11 Maths mentor and I've solved your Maths problem using a method I came up with in year 11.

Steps a and b are rearranging the two equations so that there is an equal element to both.

Step c puts the two equal equations you found in steps a and b together. You then rearrage this to get y on its own.

Step d puts the newfound y value into the equation 'x=' which you found in step a.

Step e puts your already-found x and y values into the equation you found in part b. If your answer to this is right (in this case, you get -2=-2, which is true), you know you have the right answer.

I know it's quite complex to understand at first, but I've found that it's a really reliable method which I still use for A-level Maths.

I hope this helps

P.S. Sorry the picture's sideways - I'll try and fix it
Attached Images

4. (Original post by Green22)
Thanks for that but it is just that may working out is a bit different. Maybe your answer is right though.
Oh I see what you're doing now, I've never seen anyone do a simultaneous equation that way

But if you do it your way:

12x+20y=76
12x-6y=54
20y+6y=76--54?
26y=130 (because two negatives is a positive)
y=5

Then substitute it in the original equations...

3x+5(5)=19
3x+25=19
(-25) 3x=-6
x=-2

3(-2)+5(5) -> -6+25 = 19
4(-2)-2(5) -> -8-10 = -18

5. (Original post by brittanna)
Wait, so is your problem just with working out the value of 130/26? Do you understand how to get to y=130/26?
i believe so because 76--54=130 right? the question isn non calculator btw
6. (Original post by Kangie)
Why? I even did the whole simultaneous equation and the answer is correct.
I got x to be -2
7. (Original post by Green22)
i believe so because 76--54=130 right? the question isn non calculator btw
Yeah, 76--54=76+54=130. (You could always write it out with the columns lined up if you needed to).

You could always do the following to help you work out the division:

8. Hope this is better
Attached Images

9. You guys sure do know how to to turn an easy question into a lot of working... x = -2, y = 5

10. (Original post by Green22)
Oh, i meant Kangie sorry
11. (Original post by Kangie)
Oh I see what you're doing now, I've never seen anyone do a simultaneous equation that way
There are many ways for this but my way is the way i was thought.

But if you do it your way:

12x+20y=76
12x-6y=54
20y+6y=76--54?
26y=130 (because two negatives is a positive)
y=5

Then substitute it in the original equations...

3x+5(5)=19
3x+25=19
(-25) 3x=-6
x=-2

3(-2)+5(5) -> -6+25 = 19
4(-2)-2(5) -> -8-10 = -18

I understand now. Thanks.
12. (Original post by danniegee)

Hope this is better
Thanks for this. I understand now.
13. (Original post by Green22)
Thanks for this. I understand now.
You're welcome! Good luck with your GCSE
14. (Original post by danniegee)

Hello

I'm an A2 Mathematician and Year 11 Maths mentor and I've solved your Maths problem using a method I came up with in year 11.

Steps a and b are rearranging the two equations so that there is an equal element to both.

Step c puts the two equal equations you found in steps a and b together. You then rearrage this to get y on its own.

Step d puts the newfound y value into the equation 'x=' which you found in step a.

Step e puts your already-found x and y values into the equation you found in part b. If your answer to this is right (in this case, you get -2=-2, which is true), you know you have the right answer.

I know it's quite complex to understand at first, but I've found that it's a really reliable method which I still use for A-level Maths.

I hope this helps

P.S. Sorry the picture's sideways - I'll try and fix it

Posted from TSR Mobile
15. (Original post by Blaze3211)
Oh, i meant Kangie sorry
That were my thoughts exactly.
16. (Original post by danniegee)
You're welcome! Good luck with your GCSE
Thanks but just wondering if there is even a thing as "luck"? I am not sure tbh as in maths you either know it or you dont.
17. (Original post by brittanna)
Yeah, 76--54=76+54=130. (You could always write it out with the columns lined up if you needed to).

You could always do the following to help you work out the division:

Cool.
18. I hope you understand this:

Make x the same in both equations by finding a number that has 3 and 4 as a factor, in this case 12.
Subtract both equations, so 12x - 12x becomes 0x, because of the two minus signs, 20y - -6y becomes 20y + 6y = 26y.
Also, 76 - -54 becomes 76 + 54 = 130. Therefore, 26y = 130.
130 / 26 is 5 = y.

Substitute the value of y into the equation to find x.
3x + 5y(25) = 19.
19 - 25 = -6 = 3x
Therefore, x = -6 / 3 = -2.

Finally, x = -2 and y = 5

Took me ages to type this, but hope it helps, typing on the iPad sucks :/

Posted from TSR Mobile
19. (Original post by Green22)
Thanks but just wondering if there is even a thing as "luck"? I am not sure tbh as in maths you either know it or you dont.
Well, basically. for maths anyways.
20. (Original post by Blaze3211)
Well, basically. for maths anyways.
Cool.

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