algebra

[lkpromo]

Does anyone know how to solve for X in the equation 4X^3-40X^2+100X=25? I have simplified it to 4X(X-5)^2=25.

 

[galactus]

It does not factor too nicely. See here for a cool site on cubics

http://www.1728.com/cubic.htm

You know the quadratic formula?. Well, there is one for cubics as well. It is much more complicated though.

See here for the formula:

http://www.math.vanderbilt.edu/~schectex/courses/cubic/

But, probably about the easiest way is to graph it, get an idea where the graph crosses the x-axis, and then use the Intermediate Value theorem to hone in on the roots.

Look through the first site. Click on the link in the site and you will see a cool way to step through to find the three roots. Apparently, it is how the program in the site works. I checked it and it came out to the correct roots.

This one has 3 real roots.