how to write a function for quadratic equation?
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I wrote this into matlab but it doesn't work where express x1, x2, it express only one sol in d>=0 but ploting is work in d>=0. and it's error in d<0
why it doen't work and how to fix it?
function [x1,x2] = f(a,b,c)
if a==0
x1=-c/b;
x2=-c/b;
plot(x1,0,'gx',x2,0,'gx')
hold on
fplot(@(x) a*x.^2+b*x+c)
hold off
end
d=b^2-4*a*c;
if (d>=0)&&(~(a==0))
x1=((-b-sqrt(d))/(2*a));
x2=((-b+sqrt(d))/(2*a));
plot(x1,0,'rx',x2,0,'rx')
hold on
fplot(@(x) a*x.^2+b*x+c)
hold off
elseif a==0
x1=-c/b;
x2=-c/b;
plot(x1,0,'gx',x2,0,'gx')
hold on
fplot(@(x) a*x.^2+b*x+c)
hold off
else
[x1 x2]=[]
end
4 个评论
Dyuman Joshi
2022-9-25
Why have you written the code for condition a==0 twice?
You have to include the code for condition d<0 as well.
jun
2022-9-25
Dyuman Joshi
2022-9-25
Do you want to return empty values for if any/both of the two conditions - a==0 , d<0?
jun
2022-9-25
采纳的回答
VBBV
2022-9-25
if (d>=0) & (~(a==0))
use binary operator &
11 个评论
[x1 x2] = f(4.1,10,4)
function [x1,x2] = f(a,b,c)
if a==0
x1=-c/b;
x2=-c/b;
plot(x1,0,'gx',x2,0,'gx')
hold on
fplot(@(x) a*x.^2+b*x+c)
hold off
end
d=b^2-4*a*c
if (d>=0)&&(~(a==0))
x1=((-b-sqrt(d))/(2*a));
x2=((-b+sqrt(d))/(2*a));
plot(x1,0,'rx',x2,0,'rx')
hold on
fplot(@(x) a*x.^2+b*x+c)
hold off
elseif a==0
x1=-c/b;
x2=-c/b;
plot(x1,0,'gx',x2,0,'gx')
hold on
fplot(@(x) a*x.^2+b*x+c)
hold off
else
x1 = [];
x2 = [];
end
end
Missing end keyword in the function
jun
2022-9-25
VBBV
2022-9-25
It displays both x1 and X2 values with red markers on plot.
jun
2022-9-25
[x1 x2] = f(1,0,-4)
function [x1,x2] = f(a,b,c)
if a==0
x1=-c/b;
x2=-c/b;
plot(x1,0,'gx',x2,0,'gx')
hold on
fplot(@(x) a*x.^2+b*x+c)
hold off
end
d=b^2-4*a*c
if (d>=0)&&(~(a==0))
x1=((-b-sqrt(d))/(2*a));
x2=((-b+sqrt(d))/(2*a));
plot(x1,0,'rx',x2,0,'rx')
hold on
fplot(@(x) a*x.^2+b*x+c)
hold off
elseif a==0
x1=-c/b;
x2=-c/b;
plot(x1,0,'gx',x2,0,'gx')
hold on
fplot(@(x) a*x.^2+b*x+c)
hold off
else
x1 = [];
x2 = [];
end
end
VBBV
2022-9-25
x1 and x2 values are -2 and 2 from above result. What do you get as result ?
jun
2022-9-25
result appers x1, but figure graph is well,
Dyuman Joshi
2022-9-25
Why are you repeating a piece of code? It's redundant.
jun
2022-9-26
Are you right about 'a==0'? If 'a=0', an error like this is displayed
Dyuman Joshi
2022-9-26
Let me highlight it. See the green parts, both are same.
I would suggest you to remove the top one and edit last else as
elseif d<0
function [x1,x2] = f(a,b,c)
%{
if a==0
x1=-c/b;
x2=-c/b;
plot(x1,0,'gx',x2,0,'gx')
hold on
fplot(@(x) a*x.^2+b*x+c)
hold off
end
%}
d=b^2-4*a*c
if (d>=0)&&(~(a==0))
x1=((-b-sqrt(d))/(2*a));
x2=((-b+sqrt(d))/(2*a));
plot(x1,0,'rx',x2,0,'rx')
hold on
fplot(@(x) a*x.^2+b*x+c)
hold off
%{
elseif a==0
x1=-c/b;
x2=-c/b;
plot(x1,0,'gx',x2,0,'gx')
hold on
fplot(@(x) a*x.^2+b*x+c)
hold off
%}
else
x1 = [];
x2 = [];
end
end
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