calc_root.m

matlab宝典,电子工业出版社,包含该书的源码4-6章

% script file calc_root.m
% 
% purpose:
% This program solves for the roots of a quadratic equation
% of the form a*x^2+b*x+c=0.It calcaulates the answers of 
% roots the equation posseses.
%
% Define variables:
% a       coefficient of x^2
% b       coefficient of x
% c       constant term
% x1      first root of the equation
% x2      second root of the equation

disp('This program solves for the roots of a quadratic equation');
disp('of the form a*x^2+b*x+c=0');
a=input('Enter the coefficient A:');
b=input('Enter the coefficient B:');
c=input('Enter the coefficient C:');
discriminant=b^2-4*a*c;

%如果判别式大于0
%则根据二元方程的公式得出两个不同的实数解
if discriminant>0
    x1=(-b+sqrt(discriminant))/(2*a);
x2=(-b-sqrt(discriminant))/(2*a);
%在命令窗口显示求解结果
    disp('This equation has two real roots');
    fprintf('x1=%f\n',x1);
fprintf('x2=%f\n',x2);

    %当判别式等于0，则返回两个相同的实数根
elseif discriminant==0
    x1=-b/(2*a);
    disp('This equation has two identical roots');
    fprintf('x1=x2=%f\n',x1);
    
%当判别式小于0，则返回两个虚根
else
    real_part=-b/(2*a);
    image_part=sqrt(abs(discriminant))/(2*a);
    disp('This equation has two complex roots');
    fprintf('x1=%f+i%f\n',real_part,image_part);
    fprintf('x2=%f-i%f\n',real_part,image_part);
end