The product of the polynomials (3x 2) and (-x3 – 3) is . when this product is multiplied by (3 x), the coefficient of x4 in the result is

The product of the polynomials (3x 2) and (-x3 – 3) is -3x^5-9x²
proof
(3x 2) (-x3 – 3) = -3x^5-9x²
the main rules are as follows:
if we have  ax^p  multiplying by bx^q, so we can do the calculus as
(ax^p)( bx^q)=(ab)x^p+q 

Could you make it more clear?