How do i plot this quadratic graph?

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Yaseen Noaman
Yaseen Noaman 2020-11-22
编辑： Stephan 2020-11-23
I'm trying to plot this quadratic graph. For some reason it looks like this. It's not crossing the x axis for some reason the x axis are down. I need to fix it please.
https://imgur.com/a/FEFsG0B
This is the graph and the code.
  2 个评论
Setsuna Yuuki.
Setsuna Yuuki. 2020-11-22
that depends on the values of "a" "b" and "c", perhaps those values do not allow zero crossing.
Yaseen Noaman
Yaseen Noaman 2020-11-22
They do. A is 1 b is -2 c is -4. They do cross the x axis

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回答（1 个）

Stephan
Stephan 2020-11-23
编辑：Stephan 2020-11-23
x = -10:10;
y = polyval([1 -2 -4],x);
plot(x,y)
r = roots([1 -2 -4])
text(r(1),0,'\leftarrow Root')
text(r(2),0,'\leftarrow Root')

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