Solving cubic equations using calculator

Oct 2019
8
0
planet earth
Hello everyone,
I have a polynomial Equation I want to solve using my Texas Ti-82. I have tried using (Math- Solve) and I get the first root. how can I get the 2nd and 3rd roots too?

Kind Regards
 

skeeter

Math Team
Jul 2011
3,360
1,850
Texas
why not just graph the polynomial setting the proper window for x-min and x-max to see the zeros, then use the zero function located on the calculate menu ... ?
 
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Oct 2019
8
0
planet earth
That's a way but I don't use graphic solutions. I am working with vibrations and dynamic behavior of materials so its more convenient for me to get the roots as numbers directly. Thanks for your answer btw.
 
Oct 2019
8
0
planet earth
Thank you very much I got the answer but I would really appreciate if someone could explain how to do it using Texas IT-82 since I'm going to have exam and the only allowed tool is calculator.
 

skeeter

Math Team
Jul 2011
3,360
1,850
Texas
Can you provide a specific example of a polynomial equation that you want to see solved with a TI ?
 

skipjack

Forum Staff
Dec 2006
21,480
2,470
If the equation is f(x) = 0, and the calculator tells you that x = r is a solution, calculate the coefficients of the quadratic polynomial g(x) = f(x)/(x- r), then solve g(x) = 0.
 
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mathman

Forum Staff
May 2007
6,932
774
If you have one root of a cubic, you can obtain the quadratic for the other two roots by synthetic division of the the cubic by the linear factor of the root you got.
 
Oct 2019
8
0
planet earth
Can you provide a specific example of a polynomial equation that you want to see solved with a TI ?
This polynomial equation below, I solved using TI-82 and I only got one root:
\(\displaystyle 4x^3-16000x^2+16*10^6x-3072*10^3=0\)
so got the first root as 250. How do I find the other ones, or use this root to find out other ones?
 
Oct 2019
8
0
planet earth
If the equation is f(x) = 0, and the calculator tells you that x = r is a solution, calculate the coefficients of the quadratic polynomial g(x) = f(x)/(x- r), then solve g(x) = 0.
I didn't get that how to apply that.