Final answer:
If a polynomial is prime, it cannot be factored. '5x + 13y' is a linear polynomial and is prime in the context of integer factorization, hence it cannot be factored.
Step-by-step explanation:
The statement 'If a polynomial is prime, then it cannot be factored' can be considered as an example of a valid deductive inference. In this context, 'prime' refers to a polynomial being irreducible, meaning it cannot be factored into the product of two non-constant polynomials. When assessing the second part of the question - whether the polynomial '5x + 13y' is prime - we would need to consider if there are any polynomials that when multiplied result in '5x + 13y'. As '5x + 13y' is a linear polynomial with two variables, it doesn't factor in the realm of integers, so in that sense, it can be deemed prime. Hence, if we assume the initial statement as true and agree that '5x + 13y' is prime, we can conclude that '5x + 13y' cannot be factored.