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 is sign change in the , the possible number of positive zeros of polynomial function is .

.

Since there is sign change in the the possible number of negative zeros of polynomial function is .

Hence the maximum number of real zeros of is .   

The maximum number of real zeros of is .