GCSE simultaneous equation help please

Reply 20

Green22

OP

3

Original post by Blaze3211

Why did you make the top equation negative?

Huh? please enlighten me
:confused:

Reply 21

BobLoblawLawBlog

16

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?

Reply 22

danniegee

8

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.

Follow the letters through a-e.

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 :smile:

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

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

Reply 24

Green22

OP

3

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

Reply 25

Blaze3211

11

Original post by Kangie

Why? I even did the whole simultaneous equation and the answer is correct.

I got x to be -2

Reply 26

BobLoblawLawBlog

16

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:

\frac{130}{26} = \frac{13 * 10}{13 * 2} = \frac{10}{2} = 5

Reply 27

danniegee

8

Hope this is better :wink:

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

/thread

Reply 29

Blaze3211

11

Original post by Green22

Huh? please enlighten me
:confused:

Oh, i meant Kangie sorry

Reply 30

Green22

OP

3

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.

Reply 31

Green22

OP

3

Original post by danniegee

Hope this is better :wink:

Thanks for this. I understand now.

Reply 32

danniegee

8

Original post by Green22

Thanks for this. I understand now.

You're welcome! Good luck with your GCSE :smile:

Reply 33

langlitz

17

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.

Follow the letters through a-e.

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 :smile:

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

ImageUploadedByStudent Room1419887997.762882.jpg

Posted from TSR Mobile

Reply 34

Green22

OP

3

Original post by Blaze3211

Oh, i meant Kangie sorry

That were my thoughts exactly.

Reply 35

Green22

OP

3

Original post by danniegee

You're welcome! Good luck with your GCSE :smile:

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.

Reply 36

Green22

OP

3

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:

\frac{130}{26} = \frac{13 * 10}{13 * 2} = \frac{10}{2} = 5

Cool.

Reply 37

Chittesh14

19

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

ImageUploadedByStudent Room1419895725.730572.jpg