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Why does this quadratic expression have three zeroes?


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$begingroup$


Why does this quadratic expression have three zeroes? I understand that when coefficient of $x^2$, coefficient of $x$, and constant term becomes zero, it becomes an identity and has infinitely many solutions (when equates to zero).
But this quadratic expression, it’s coefficients are very small, but they are definitely not equal to zero. Why does this expression have three zeroes then?



enter image description here










share|cite|improve this question









$endgroup$












  • $begingroup$
    It doesn't: $2.5^2 - 5 times 2.5 + 6 = -1/4 neq 0$.
    $endgroup$
    – SampleTime
    9 hours ago










  • $begingroup$
    Try $ 0.001left(xcdot x-5x+6right)=0$ instead
    $endgroup$
    – lhf
    9 hours ago






  • 3




    $begingroup$
    It doesn't. I think the software is trying to show two zeros and the vertex. But the vertex is sufficiently close to 0 (it is -0.0025), that it has rounded to 0 in the display.
    $endgroup$
    – Doug M
    9 hours ago










  • $begingroup$
    Yeah, thanks. I just plugged in 2.5 for $x$ and got (-0.00025) I got confused when I first saw this. Because our maths teacher recently taught us about identities (when all the coefficients are zero).
    $endgroup$
    – π times e
    9 hours ago












  • $begingroup$
    If in doubt, zoom in! Desmos has pretty good resolution and will warn you when you might see a rendering error.
    $endgroup$
    – Jam
    9 hours ago


















2












$begingroup$


Why does this quadratic expression have three zeroes? I understand that when coefficient of $x^2$, coefficient of $x$, and constant term becomes zero, it becomes an identity and has infinitely many solutions (when equates to zero).
But this quadratic expression, it’s coefficients are very small, but they are definitely not equal to zero. Why does this expression have three zeroes then?



enter image description here










share|cite|improve this question









$endgroup$












  • $begingroup$
    It doesn't: $2.5^2 - 5 times 2.5 + 6 = -1/4 neq 0$.
    $endgroup$
    – SampleTime
    9 hours ago










  • $begingroup$
    Try $ 0.001left(xcdot x-5x+6right)=0$ instead
    $endgroup$
    – lhf
    9 hours ago






  • 3




    $begingroup$
    It doesn't. I think the software is trying to show two zeros and the vertex. But the vertex is sufficiently close to 0 (it is -0.0025), that it has rounded to 0 in the display.
    $endgroup$
    – Doug M
    9 hours ago










  • $begingroup$
    Yeah, thanks. I just plugged in 2.5 for $x$ and got (-0.00025) I got confused when I first saw this. Because our maths teacher recently taught us about identities (when all the coefficients are zero).
    $endgroup$
    – π times e
    9 hours ago












  • $begingroup$
    If in doubt, zoom in! Desmos has pretty good resolution and will warn you when you might see a rendering error.
    $endgroup$
    – Jam
    9 hours ago














2












2








2





$begingroup$


Why does this quadratic expression have three zeroes? I understand that when coefficient of $x^2$, coefficient of $x$, and constant term becomes zero, it becomes an identity and has infinitely many solutions (when equates to zero).
But this quadratic expression, it’s coefficients are very small, but they are definitely not equal to zero. Why does this expression have three zeroes then?



enter image description here










share|cite|improve this question









$endgroup$




Why does this quadratic expression have three zeroes? I understand that when coefficient of $x^2$, coefficient of $x$, and constant term becomes zero, it becomes an identity and has infinitely many solutions (when equates to zero).
But this quadratic expression, it’s coefficients are very small, but they are definitely not equal to zero. Why does this expression have three zeroes then?



enter image description here







roots quadratics






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked 9 hours ago









π times eπ times e

1492 silver badges9 bronze badges




1492 silver badges9 bronze badges












  • $begingroup$
    It doesn't: $2.5^2 - 5 times 2.5 + 6 = -1/4 neq 0$.
    $endgroup$
    – SampleTime
    9 hours ago










  • $begingroup$
    Try $ 0.001left(xcdot x-5x+6right)=0$ instead
    $endgroup$
    – lhf
    9 hours ago






  • 3




    $begingroup$
    It doesn't. I think the software is trying to show two zeros and the vertex. But the vertex is sufficiently close to 0 (it is -0.0025), that it has rounded to 0 in the display.
    $endgroup$
    – Doug M
    9 hours ago










  • $begingroup$
    Yeah, thanks. I just plugged in 2.5 for $x$ and got (-0.00025) I got confused when I first saw this. Because our maths teacher recently taught us about identities (when all the coefficients are zero).
    $endgroup$
    – π times e
    9 hours ago












  • $begingroup$
    If in doubt, zoom in! Desmos has pretty good resolution and will warn you when you might see a rendering error.
    $endgroup$
    – Jam
    9 hours ago


















  • $begingroup$
    It doesn't: $2.5^2 - 5 times 2.5 + 6 = -1/4 neq 0$.
    $endgroup$
    – SampleTime
    9 hours ago










  • $begingroup$
    Try $ 0.001left(xcdot x-5x+6right)=0$ instead
    $endgroup$
    – lhf
    9 hours ago






  • 3




    $begingroup$
    It doesn't. I think the software is trying to show two zeros and the vertex. But the vertex is sufficiently close to 0 (it is -0.0025), that it has rounded to 0 in the display.
    $endgroup$
    – Doug M
    9 hours ago










  • $begingroup$
    Yeah, thanks. I just plugged in 2.5 for $x$ and got (-0.00025) I got confused when I first saw this. Because our maths teacher recently taught us about identities (when all the coefficients are zero).
    $endgroup$
    – π times e
    9 hours ago












  • $begingroup$
    If in doubt, zoom in! Desmos has pretty good resolution and will warn you when you might see a rendering error.
    $endgroup$
    – Jam
    9 hours ago
















$begingroup$
It doesn't: $2.5^2 - 5 times 2.5 + 6 = -1/4 neq 0$.
$endgroup$
– SampleTime
9 hours ago




$begingroup$
It doesn't: $2.5^2 - 5 times 2.5 + 6 = -1/4 neq 0$.
$endgroup$
– SampleTime
9 hours ago












$begingroup$
Try $ 0.001left(xcdot x-5x+6right)=0$ instead
$endgroup$
– lhf
9 hours ago




$begingroup$
Try $ 0.001left(xcdot x-5x+6right)=0$ instead
$endgroup$
– lhf
9 hours ago




3




3




$begingroup$
It doesn't. I think the software is trying to show two zeros and the vertex. But the vertex is sufficiently close to 0 (it is -0.0025), that it has rounded to 0 in the display.
$endgroup$
– Doug M
9 hours ago




$begingroup$
It doesn't. I think the software is trying to show two zeros and the vertex. But the vertex is sufficiently close to 0 (it is -0.0025), that it has rounded to 0 in the display.
$endgroup$
– Doug M
9 hours ago












$begingroup$
Yeah, thanks. I just plugged in 2.5 for $x$ and got (-0.00025) I got confused when I first saw this. Because our maths teacher recently taught us about identities (when all the coefficients are zero).
$endgroup$
– π times e
9 hours ago






$begingroup$
Yeah, thanks. I just plugged in 2.5 for $x$ and got (-0.00025) I got confused when I first saw this. Because our maths teacher recently taught us about identities (when all the coefficients are zero).
$endgroup$
– π times e
9 hours ago














$begingroup$
If in doubt, zoom in! Desmos has pretty good resolution and will warn you when you might see a rendering error.
$endgroup$
– Jam
9 hours ago




$begingroup$
If in doubt, zoom in! Desmos has pretty good resolution and will warn you when you might see a rendering error.
$endgroup$
– Jam
9 hours ago










3 Answers
3






active

oldest

votes


















3












$begingroup$

There are zeros at $(2,0)$ and $(3,0)$



The other point of $(2.5,-0.00025)$ is not a zero, but may have been shown rounded; it is the minimum and also the vertex of the parabola






share|cite|improve this answer









$endgroup$













  • $begingroup$
    I just put 2.5 for 𝑥 and got (-0.00025) Actually I got confused when I first saw this. Our maths teacher recently taught us about identities, when all the coefficients are zero. So I was just playing with different numbers, wondering what would happen if all the coefficients became very small but still non-zero. I was so startled when I saw this expression, that I forgot to plug 2.5 for x and check if I got zero, lol. And thanks
    $endgroup$
    – π times e
    9 hours ago





















3












$begingroup$

It is not. Possibly a rounding error. Zeroes for that polynomial are at $x=2$ and $x=3$
There is a minimum at $x=2.5$, hitting the value -0.00025, which is also a possible reason why the point is highlighted






share|cite|improve this answer











$endgroup$













  • $begingroup$
    Plugging in 2.5 for $x$ gets us ($0.01225$ - $0.01250$), which is not equal to zero. I just noticed it. Thanks for clarifying
    $endgroup$
    – π times e
    9 hours ago





















2












$begingroup$

It cannot have more than 2 zeros. The fundamental theorem of algebra tells us it has exactly 2 zeros, possibly repeated.
The zeros of
$$
c(x^2-5x+6)
$$

where $c$ is any (non-zero) constant, are the same as the zeros of,
$$
(x^2-5x+6)
$$

What you are running in to is the real-life practicalities of using a computational tool to determine the zeros. The plot you show displays the $y$ values with no decimal places. Things to try



[1] Can you display the $y$ to more decimal places?



[2] Can you change the scales of the plot to get a better look?






share|cite|improve this answer









$endgroup$
















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    3 Answers
    3






    active

    oldest

    votes








    3 Answers
    3






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    3












    $begingroup$

    There are zeros at $(2,0)$ and $(3,0)$



    The other point of $(2.5,-0.00025)$ is not a zero, but may have been shown rounded; it is the minimum and also the vertex of the parabola






    share|cite|improve this answer









    $endgroup$













    • $begingroup$
      I just put 2.5 for 𝑥 and got (-0.00025) Actually I got confused when I first saw this. Our maths teacher recently taught us about identities, when all the coefficients are zero. So I was just playing with different numbers, wondering what would happen if all the coefficients became very small but still non-zero. I was so startled when I saw this expression, that I forgot to plug 2.5 for x and check if I got zero, lol. And thanks
      $endgroup$
      – π times e
      9 hours ago


















    3












    $begingroup$

    There are zeros at $(2,0)$ and $(3,0)$



    The other point of $(2.5,-0.00025)$ is not a zero, but may have been shown rounded; it is the minimum and also the vertex of the parabola






    share|cite|improve this answer









    $endgroup$













    • $begingroup$
      I just put 2.5 for 𝑥 and got (-0.00025) Actually I got confused when I first saw this. Our maths teacher recently taught us about identities, when all the coefficients are zero. So I was just playing with different numbers, wondering what would happen if all the coefficients became very small but still non-zero. I was so startled when I saw this expression, that I forgot to plug 2.5 for x and check if I got zero, lol. And thanks
      $endgroup$
      – π times e
      9 hours ago
















    3












    3








    3





    $begingroup$

    There are zeros at $(2,0)$ and $(3,0)$



    The other point of $(2.5,-0.00025)$ is not a zero, but may have been shown rounded; it is the minimum and also the vertex of the parabola






    share|cite|improve this answer









    $endgroup$



    There are zeros at $(2,0)$ and $(3,0)$



    The other point of $(2.5,-0.00025)$ is not a zero, but may have been shown rounded; it is the minimum and also the vertex of the parabola







    share|cite|improve this answer












    share|cite|improve this answer



    share|cite|improve this answer










    answered 9 hours ago









    HenryHenry

    105k4 gold badges85 silver badges173 bronze badges




    105k4 gold badges85 silver badges173 bronze badges












    • $begingroup$
      I just put 2.5 for 𝑥 and got (-0.00025) Actually I got confused when I first saw this. Our maths teacher recently taught us about identities, when all the coefficients are zero. So I was just playing with different numbers, wondering what would happen if all the coefficients became very small but still non-zero. I was so startled when I saw this expression, that I forgot to plug 2.5 for x and check if I got zero, lol. And thanks
      $endgroup$
      – π times e
      9 hours ago




















    • $begingroup$
      I just put 2.5 for 𝑥 and got (-0.00025) Actually I got confused when I first saw this. Our maths teacher recently taught us about identities, when all the coefficients are zero. So I was just playing with different numbers, wondering what would happen if all the coefficients became very small but still non-zero. I was so startled when I saw this expression, that I forgot to plug 2.5 for x and check if I got zero, lol. And thanks
      $endgroup$
      – π times e
      9 hours ago


















    $begingroup$
    I just put 2.5 for 𝑥 and got (-0.00025) Actually I got confused when I first saw this. Our maths teacher recently taught us about identities, when all the coefficients are zero. So I was just playing with different numbers, wondering what would happen if all the coefficients became very small but still non-zero. I was so startled when I saw this expression, that I forgot to plug 2.5 for x and check if I got zero, lol. And thanks
    $endgroup$
    – π times e
    9 hours ago






    $begingroup$
    I just put 2.5 for 𝑥 and got (-0.00025) Actually I got confused when I first saw this. Our maths teacher recently taught us about identities, when all the coefficients are zero. So I was just playing with different numbers, wondering what would happen if all the coefficients became very small but still non-zero. I was so startled when I saw this expression, that I forgot to plug 2.5 for x and check if I got zero, lol. And thanks
    $endgroup$
    – π times e
    9 hours ago















    3












    $begingroup$

    It is not. Possibly a rounding error. Zeroes for that polynomial are at $x=2$ and $x=3$
    There is a minimum at $x=2.5$, hitting the value -0.00025, which is also a possible reason why the point is highlighted






    share|cite|improve this answer











    $endgroup$













    • $begingroup$
      Plugging in 2.5 for $x$ gets us ($0.01225$ - $0.01250$), which is not equal to zero. I just noticed it. Thanks for clarifying
      $endgroup$
      – π times e
      9 hours ago


















    3












    $begingroup$

    It is not. Possibly a rounding error. Zeroes for that polynomial are at $x=2$ and $x=3$
    There is a minimum at $x=2.5$, hitting the value -0.00025, which is also a possible reason why the point is highlighted






    share|cite|improve this answer











    $endgroup$













    • $begingroup$
      Plugging in 2.5 for $x$ gets us ($0.01225$ - $0.01250$), which is not equal to zero. I just noticed it. Thanks for clarifying
      $endgroup$
      – π times e
      9 hours ago
















    3












    3








    3





    $begingroup$

    It is not. Possibly a rounding error. Zeroes for that polynomial are at $x=2$ and $x=3$
    There is a minimum at $x=2.5$, hitting the value -0.00025, which is also a possible reason why the point is highlighted






    share|cite|improve this answer











    $endgroup$



    It is not. Possibly a rounding error. Zeroes for that polynomial are at $x=2$ and $x=3$
    There is a minimum at $x=2.5$, hitting the value -0.00025, which is also a possible reason why the point is highlighted







    share|cite|improve this answer














    share|cite|improve this answer



    share|cite|improve this answer








    edited 9 hours ago

























    answered 9 hours ago









    DavidDavid

    77410 bronze badges




    77410 bronze badges












    • $begingroup$
      Plugging in 2.5 for $x$ gets us ($0.01225$ - $0.01250$), which is not equal to zero. I just noticed it. Thanks for clarifying
      $endgroup$
      – π times e
      9 hours ago




















    • $begingroup$
      Plugging in 2.5 for $x$ gets us ($0.01225$ - $0.01250$), which is not equal to zero. I just noticed it. Thanks for clarifying
      $endgroup$
      – π times e
      9 hours ago


















    $begingroup$
    Plugging in 2.5 for $x$ gets us ($0.01225$ - $0.01250$), which is not equal to zero. I just noticed it. Thanks for clarifying
    $endgroup$
    – π times e
    9 hours ago






    $begingroup$
    Plugging in 2.5 for $x$ gets us ($0.01225$ - $0.01250$), which is not equal to zero. I just noticed it. Thanks for clarifying
    $endgroup$
    – π times e
    9 hours ago













    2












    $begingroup$

    It cannot have more than 2 zeros. The fundamental theorem of algebra tells us it has exactly 2 zeros, possibly repeated.
    The zeros of
    $$
    c(x^2-5x+6)
    $$

    where $c$ is any (non-zero) constant, are the same as the zeros of,
    $$
    (x^2-5x+6)
    $$

    What you are running in to is the real-life practicalities of using a computational tool to determine the zeros. The plot you show displays the $y$ values with no decimal places. Things to try



    [1] Can you display the $y$ to more decimal places?



    [2] Can you change the scales of the plot to get a better look?






    share|cite|improve this answer









    $endgroup$


















      2












      $begingroup$

      It cannot have more than 2 zeros. The fundamental theorem of algebra tells us it has exactly 2 zeros, possibly repeated.
      The zeros of
      $$
      c(x^2-5x+6)
      $$

      where $c$ is any (non-zero) constant, are the same as the zeros of,
      $$
      (x^2-5x+6)
      $$

      What you are running in to is the real-life practicalities of using a computational tool to determine the zeros. The plot you show displays the $y$ values with no decimal places. Things to try



      [1] Can you display the $y$ to more decimal places?



      [2] Can you change the scales of the plot to get a better look?






      share|cite|improve this answer









      $endgroup$
















        2












        2








        2





        $begingroup$

        It cannot have more than 2 zeros. The fundamental theorem of algebra tells us it has exactly 2 zeros, possibly repeated.
        The zeros of
        $$
        c(x^2-5x+6)
        $$

        where $c$ is any (non-zero) constant, are the same as the zeros of,
        $$
        (x^2-5x+6)
        $$

        What you are running in to is the real-life practicalities of using a computational tool to determine the zeros. The plot you show displays the $y$ values with no decimal places. Things to try



        [1] Can you display the $y$ to more decimal places?



        [2] Can you change the scales of the plot to get a better look?






        share|cite|improve this answer









        $endgroup$



        It cannot have more than 2 zeros. The fundamental theorem of algebra tells us it has exactly 2 zeros, possibly repeated.
        The zeros of
        $$
        c(x^2-5x+6)
        $$

        where $c$ is any (non-zero) constant, are the same as the zeros of,
        $$
        (x^2-5x+6)
        $$

        What you are running in to is the real-life practicalities of using a computational tool to determine the zeros. The plot you show displays the $y$ values with no decimal places. Things to try



        [1] Can you display the $y$ to more decimal places?



        [2] Can you change the scales of the plot to get a better look?







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered 9 hours ago









        PM.PM.

        3,6182 gold badges9 silver badges25 bronze badges




        3,6182 gold badges9 silver badges25 bronze badges






























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