How to solve three degree equation

Mmm,

Mat's first method is for equations on degree 2

Factorization method can be used if you can work out the factors.  

You can use remainder theorem / factor theroem to help find them.

https://www.khanacademy.org/math/algebra2/polynomial_and_rational/polynomial-remainder-theorem-tutorial/v/polynomial-remainder-theorem

You can use graphing with an online graphing program such as Desmos.

you can use an online calculator such as our web2calc  one or Wolfram|Alpha

If you give an exact example then we can better direct you :)

there is 3 methods they are

-b+(or)-sqrt of b^2-4ac/2a

              or

fatrization method

              or 

elimination method

choose ur method which u feel gud

Have a look at https://en.wikipedia.org/wiki/Cubic_function for the analytical solution to a general cubic equation.

.