can u tell me how to solve a cubic or higher degree polynomial to obtain its roots with eg.??

there's no method to find roots of cubic equations..

Step 1

Try finding atleast one root by hit and trial(you may try 1.-1,0,2,-2 and some values)..and after finding one root find others by factorisation..if you want me to tell you the factorisation method..please do ask for it,