function [x1 x2]=equationSolve(a,b,c)
%[x1 x2] is return value
%a,b,c are input parameters
%calculate quadratic equation with one unknown
delt=b*b-4*a*c;
if delt<0
'no answer';
elseif delt==0
'only one answer';
x1=-a/2;
else
x1=(-a+sqrt(delt))/2;
x2=(-a-sqrt(delt))/2;
end保存为equationSolve.m，加入到matlab的path中，就可以直接用了。
原文：http://blog.csdn.net/chuchus/article/details/44727071