The polynomial function is .

The maximum number of real zeros of a polynomial function is equal to the degree of that polynomial function.

So the maximum number of real zeros of is .

Descartes rule of signs is useful for finding the maximum number of real zeros of the polynomial function.

Descartes sign rule :

The possible number of positive zeros of polynomial function is the number of sign changes of the coefficients of or that number minus even number.

.

Since there are sign changes in the the possible number of positive zeros of polynomial function is .

Since there are sign changes in the the possible number of  positive zeros of polynomial function is .

Hence, by Descartes sign rule, the maximum number of zeros is .

The maximum number of real zeros of is .