You may want to review adding polynomials first.

To multiply a polynomial by a monomial, you need to
multiply *each* term of the polynomial by the monomial. For
example, suppose you want to multiply
2*x*(2*x*^{2} − 3). Then the answer is
2*x*(2*x*^{2}) − 2*x*(3), or
4*x*^{3} − 6*x*.