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# solving simultaneous linear equations graphically

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1. I currently don't understand how to solve these graphically.
I tried my best and I just need someone to explain it X thank you!

Equation is: x+y=5 and X-y=1

Thank you so much!!!
2. (Original post by z_o_e)
I currently don't understand how to solve these graphically.
I tried my best and I just need someone to explain it X thank you!

Equation is: x+y=5 and X-y=1

Thank you so much!!!
Plot both graphs. The solution is where the lines cross/meet.
Hope this helps
3. (Original post by geekmillie)
Plot both graphs. The solution is where the lines cross/meet.
Hope this helps
How do I plot them? I'm so sorry!!!

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4. find out all the x and y values for each equation, draw out the lines on the graph and where the lines meet the coordinates are the answer e.g. (x, y) (6, 12) so x = 6 and y = 12
5. (Original post by hello654321)
find out all the x and y values for each equation, draw out the lines on the graph and where the lines meet the coordinates are the answer e.g. (x, y) (6, 12) so x = 6 and y = 12
Something like this?

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6. (Original post by z_o_e)
Something like this?

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Yep, so you know that two points on the graph are (0,5) and (5,0), which you plot and then you draw a line through these two points.
7. (Original post by TheOtherSide.)
Yep, so you know that two points on the graph are (0,5) and (5,0), which you plot and then you draw a line through these two points.
I got this!

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8. (Original post by z_o_e)
I got this!

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I think you plotted x - y = 1 wrong - if you rearrange this equation, you get y = x + 1, which tells you that the y-intercept is at (0,1) but the other line is correct!
9. (Original post by TheOtherSide.)
I think you plotted x - y = 1 wrong - if you rearrange this equation, you get y = x + 1, which tells you that the y-intercept is at (0,1) but the other line is correct!
I got this for the second question

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10. (Original post by z_o_e)
I got this for the second question

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What were the equations for those two lines?

Plus I just realised that with 'x + y = 5', the line didn't go through (5,0)
11. (Original post by TheOtherSide.)
What were the equations for those two lines?

Plus I just realised that with 'x + y = 5', the line didn't go through (5,0)
It's the second one.

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12. (Original post by z_o_e)
It's the second one.

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With '2x - y = 9' the line should go through the points (0,-9) and (4.5,0). Try changing the numbers on the axes.

And the other line doesn't look completely diagonal - it should pass through the points (1,1), (2,2) and so on.
13. (Original post by TheOtherSide.)
With '2x - y = 9' the line should go through the points (0,-9) and (4.5,0). Try changing the numbers on the axes.

And the other line doesn't look completely diagonal - it should pass through the points (1,1), (2,2) and so on.
Oh no!!!

I'm trying to figure the first one out again. I didn't completey understand.
This is how I done the equations.

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14. (Original post by z_o_e)
Oh no!!!

I'm trying to figure the first one out again. I didn't completey understand.
This is how I done the equations.

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With the first equation, your calculations were correct. You just need to look back on where you plotted the points.

And with the second equation, your answer for y was incorrect. Remember that two negatives make a positive, meaning that y has to be -1.
15. (Original post by TheOtherSide.)
With the first equation, your calculations were correct. You just need to look back on where you plotted the points.

And with the second equation, your answer for y was incorrect. Remember that two negatives make a positive, meaning that y has to be -1.
Thank you so so much!!!

Here I did it again

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16. (Original post by z_o_e)
Thank you so so much!!!

Here I did it again

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Oh wait, I see what you're doing! The values you got for x and y are parts of two different points! For example, with the first question, the line x + y = 5, two points that are on the line are (0,5) and (5,0) and this is all for one line.

With x - y = 1, you'd get the points (1,0) and (0,-1) which are part of a different line.
17. (Original post by TheOtherSide.)
Oh wait, I see what you're doing! The values you got for x and y are parts of two different points! For example, with the first question, the line x + y = 5, two points that are on the line are (0,5) and (5,0) and this is all for one line.

With x - y = 1, you'd get the points (1,0) and (0,-1) which are part of a different line.
Ooooh! !!!!!!

I got this

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18. This would have been so useful for the first Edexcel paper
19. (Original post by z_o_e)
Ooooh! !!!!!!

I got this

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You are so close! For the second line, remember that the first number in the brackets, like (1,0) is the x value, so it's at 1 along the horizontal axis, and then the vertical axis for the second number in the brackets.
20. (Original post by TheOtherSide.)
You are so close! For the second line, remember that the first number in the brackets, like (1,0) is the x value, so it's at 1 along the horizontal axis, and then the vertical axis for the second number in the brackets.
I don't understand this!!!!!!!

I got like two opposite points and the line doesn't go across them.

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