Write a program in a script file that determines the real roots of a quadratic equation

Howdy, I am new to math lab and need a little help The question asks: "Write a program in a script file that determines the real roots of a quadratic equation ax^2+bx+c=0. Name the file quadroots. When the file runs, it asks the user to input values of the constants a,b, and c. To calculate the roots of the equation the program calculates the discriminant D, given by D=b^2-4ac."

Then it goes on to give me specific equations and what Matlab is actually doing

I don't know what commands to use, and any help would be appreciated, thanks

[Seth]

Technically, I have nothing since I don't know where to start. it seems so simple. But i don't know what commands to use

Answer 1

[Thomas]

If you are beginning, this is a good resource. It is a MATLAB tutorial and will help you solve quadratic equations with MATLAB.

http://www.tufts.edu/~rwhite07/Matlab.html

Answer 2

[Sean de Wolski]

doc roots

and, specifically:

roots([a b c]);

Answer 3

[Fikru Dikumbab]

% ax^2+bx+c =0 is a quadratic equation

function qadr(a,b,c)

if b^2-4*a*c > 0

   r1=(-b+sqrt(b^2-4*a*c))/2*a

   r2=(-b-sqrt(b^2-4*a*c))/2*a

else if b^2-4*a*c == 0

   r=-b/2*a

   else

disp(' No real solution')

   end

end

end

Answer 4

[Md. Intesar Farhan Labib]

clc 
clear all
close all
a= input("Co-efficient of x^2: ");
b= input("Co-efficient of x: ");
c=input("Contant term: ");
d= b^2-4*a*c;
fx=[a b c];
x=roots(fx);
if d>0
disp(['The equation has two roots ', num2str(x(1)),' ,',num2str(x(2))]);
elseif d==0
disp(['The equation has one root ', num2str(x(1)),',',num2str(x(2))]);
else
 disp("The equation has no real roots.");
 end

[Chandrachud Shrivastava]

```

clc 
clear all
close all
a= input("Co-efficient of x^2: ");
b= input("Co-efficient of x: ");
c=input("Contant term: ");
d= b^2-4*a*c;
fx=[a b c];
x=roots(fx);
if d>0
    fprintf(['The equation has two roots ', num2str(x(1)),' ,',num2str(x(2))]);
elseif d==0
    fprintf(['The equation has one root ', num2str(x(1)),',',num2str(x(2))]);
else
    x1 = (-b + sqrt (d)) / (2*a);
    x2 = (-b - sqrt (d)) / (2*a);
    fprintf('Complex Zeros: %g + i*%g, %g + i*%g\n',real(x1),imag(x1),real(x2),imag(x2))
end

```

[Shailendra Shankar]

@Chandrachud Shrivastava @Md. Intesar Farhan Labib

How can I modify your programs for the below conditions:

1. IF a = 0 and b ≠ 0, the equation will be linear, and there will be one root, x = - c/b and the same should be printed in the command window.
2. IF both a and b are equal to 0, then the equation is invalid and the same should be printed in the command window.

below is the error I get:

Index exceeds the number of array elements. Index must not exceed 1.

Error in QUAD (line 11)

disp(['The equation has two roots ', num2str(x(1)),',',num2str(x(2))]);

[Md. Intesar Farhan Labib]

You can add additional command before checking D. First check whether a= 0 or not. If a=0 and b=0 Then display that the input is invalid. elseif a=0 Then simply show the result as -c/b Else The rest of the programme should be written here.

Thanks

[Shailendra Shankar]

clc

clear all

close all

a= input("Co-efficient of x^2: ");

b= input("Co-efficient of x: ");

c= input("Contant term: ");

d= b^2-4*a*c;

if a==0&&b==0;

disp ('The equation is invalid')

elseif a==0

x=-c/b;

disp('The equation is now linear and has one root',x);

end

fx=[a b c];

x=roots(fx);

if d>0

disp('The equation has two roots ', num2str(x(1)),',',num2str(x(2)));

elseif d==0

disp('The equation has one root ', num2str(x(1)));

else

disp('The equation has no real roots.');

end

Can you correct this code for me please.

ERROR MSG:

Co-efficient of x^2: 0

Co-efficient of x: 4

Contant term: -16

Error using disp

Too many input arguments.

Error in QUAD (line 12)

disp('The equation is now linear and has one root',x);

[Shailendra Shankar]

Here are my requirements:

1. need to show that if a=b=0, the equation is invalid
2. if a=0, the equation is linear and the root is to be displayed
3. if d>0, the equation has two roots which have to be displayed
4. if d=0, the equation has only one root which has to be displayed
5. if d<0, the equation has no real roots

Answer 5

[Matt Kindig]

What do you have so far?

[Seth]

Technically, I have nothing since I don't know where to start. it seems so simple. But i don't know what commands to use

Answer 6

[Matt Kindig]

Well let's break down the question step by step, with the specified section of the documentation for each.

1. Get input a, b, c from user
2. Calculate discriminant D
3. Compare D to 0.
4. If D < 0, there will be imaginary roots. Since your assignment specifies real roots, throw an error here. If D == 0, there will be one root. If D > 0, there will be two roots.
5. Calculate the roots using the quadratic formula.
6. Display results to user or output (depending on assignment specification).

For step 1, look at the 'input' function in MATLAB. The rest of the assignment can be done using straightforward arithmetic operations (+,-,*,/). For steps 3-4, use an if-else structure.

This should get you started...