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    I've used the X-axis in a question as y=1x+0, and got the right answer but with the wrong sign? Please can someone tell me if I have made a mistake with this equation? Thank you
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    The x axis is y=0.

    y=x is the identity function represented by a diagonal line inclined at \frac{\pi}{4} radians or 45^{\circ} from the axes.
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    (Original post by jazz_xox_)
    I've used the X-axis in a question as y=1x+0, and got the right answer but with the wrong sign? Please can someone tell me if I have made a mistake with this equation? Thank you
    At every single point on the x axis, y is equal to zero. So the equation for the x axis is y=0 not y=x.
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    (Original post by Plagioclase)
    At every single point on the x axis, y is equal to zero. So the equation for the x axis is y=0 not y=x.
    Thank you, I'm trying to use it in simultaneous equations with 4y=2x+23 but not sure how to cancel them by this method?


    Edit: I think I've got it now by using y=0x+0, but my answer still has the wrong sign...
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    (Original post by jazz_xox_)
    Thank you, I'm trying to use it in simultaneous equations with 4y=2x+23 but not sure how to cancel them by this method?


    Edit: I think I've got it now by using y=0x+0, but my answer still has the wrong sign...
    If your simultaneous equations are 4y=2x+23 and y=0, substitute y=0 into the first equation to get 0=2x+23 which you should then be able to solve.
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    (Original post by Plagioclase)
    If your simultaneous equations are 4y=2x+23 and y=0, substitute y=0 into the first equation to get 0=2x+23 which you should then be able to solve.
    Fab thank you! Do you know why I was getting the wrong sign by doing it with elimination? - I got my answer as 23/2 rather than -23/2
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    (Original post by jazz_xox_)
    Fab thank you! Do you know why I was getting the wrong sign by doing it with elimination? - I got my answer as 23/2 rather than -23/2
    Remember, you need to do the same thing to both sides of the equation. We want the x to be by itself so we subtract 23 from both sides to get 0-23 = 2x + 23 - 23 \longrightarrow 2x = -23 \longrightarrow  x = -\frac{23}{2}.
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    (Original post by Plagioclase)
    Remember, you need to do the same thing to both sides of the equation. We want the x to be by itself so we subtract 23 from both sides to get 0-23 = 2x + 23 - 23 \longrightarrow 2x = -23 \longrightarrow  x = -\frac{23}{2}.
    Thank you very much .
 
 
 
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