c:=12+10x^4+7x^3-89x^2+65x+4sinx

how do i plot a graph of c,

calculate the roots and check the correctness of all found roots.

Thanks for your kind solutions in advance.

Check the correctness of the solution by substituting for all found roots.

This are my found roots:

a:=12+10x^4+7x^3-89x^2+65x

and i found my roots (e.g);

b:= -3.5666666666,1.238969999,5.7777777,8888888888