Question 1199134
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Vieta's formula / (theorem) for quadratic equation.



See and learn from these sources


https://www.andrew.cmu.edu/user/daltizio/Vietas%20Formulas.pdf
https://en.wikipedia.org/wiki/Vieta%27s_formulas#:~:text=In%20mathematics%2C%20Vieta's%20formulas%20relate,%2C%20%22Franciscus%20Vieta%22).



About French mathematician Francois Vieta read from this Wikipedia article


https://en.wikipedia.org/wiki/Fran%C3%A7ois_Vi%C3%A8te



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To see many typical solved problems on  Vieta's theorem,  look into the lesson

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/quadratic/lessons/Using-Vieta%27s-theorem-to-solve-qudratic-equations.lesson>Using Vieta's theorem to solve qudratic equations and related problems</A>

in this site.


Also, &nbsp;you have this free of charge online textbook in ALGEBRA-I in this site

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson>ALGEBRA-I - YOUR ONLINE TEXTBOOK</A>.


The referred lessons are the part of this textbook under the topic &nbsp;"<U>Quadratic equations</U>". 



Save the link to this online textbook together with its description


Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson


to your archive and use it when it is needed.