friend what the iitian from kharagpur said is absolutely correct.

just i m not getting 1 thing.

acc. to me the no of changes in sign by putting +x gives +ve roots and no changes in sign by putting x=-x gives -ve roots if the sum of no of +ve and -ve roots is less than the degree of polynomial then the remaining roots r complex.+ve and -ve roots include all real no rational as well as irrational.