Question

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Explanation:

1. When multiplying a monomial by a polynomial, after applying the distributive property, we combine like terms to simplify the resulting expression.
2. The leading term of a polynomial is defined as the term with the highest degree of the variable.
3. The distributive property states that $a(b+c)=ab+ac$, which matches the structure: $x(x^2+4) + 3x(x^2+4) = (x+3x)(x^2+4)$, demonstrating the reverse of the distributive (factoring) form, which is still an application of the distributive property.

Answer:

1. like terms
2. leading
3. distributive