Question

The product of a constant factor 15 and a 2-term factor x+4

Answer 1

The product of 15 and $x+4$ is $15(x+4) = 15x+60$. This is a linear binomial.

$4x^3-2x-9-(2x^3)$ is a cubic trinomial. In your original question, I'm not sure what the $5x+3$ means.