Without using the roots command, write a function to calculate roots of the quadratic equation

Without using the roots command, write a function to calculate roots of the quadratic equation

ax^2+bx+c=0

Inputs to the function should be the coefficients a, b and c and output should be the roots. Test your program by setting a=2,b=3,c=-1

can someone help me out with this? I cant think of anything but roots to use. would I have to use poly? or fzero?

Answer 1

[Evan]

No need to call any built-in function. Just write your own using the quadratic formula.

Answer 2

[Tom]

I'd recommend maths.

Answer 3

[James Tursa]

You can use one of the formulations here:

http://en.wikipedia.org/wiki/Quadratic_equation

The quadratic formula is listed, of course, but that is prone to cancellation error. So I would advise impressing your professor by coding up the algorithm under the "Avoiding loss of significance" section.

[Chris]

This confuses me still how do I add in an Algorithm? Im terrible at this matlab stuff. so would i have to put the original function in?

[James Tursa]

It would be best if you could post what you have so far and then we can comment on it and suggest improvements. E.g., a function outline would be this (e.g., put in a file called quadratic_roots.m):

function [x1 x2] = quadratic_roots(a,b,c)

% add your code here to calculate x1 and x2

return
end