Final answer:
To multiply the given polynomials, use the distributive property and combine like terms to simplify the expression.
Step-by-step explanation:
To multiply the polynomials (a + 3a - 7) and (2a - a + 4), we can use the distributive property. We multiply each term of the first polynomial by each term of the second polynomial, and then combine like terms.
(a + 3a - 7) * (2a - a + 4) = a * 2a + a * (-a) + a * 4 + 3a * 2a + 3a * (-a) + 3a * 4 - 7 * 2a - 7 * (-a) - 7 * 4
Simplifying the expression, we get 2a^2 - a^2 + 4a + 6a^2 - 3a - 21a - 14a + 7
Combining like terms, the final simplified answer is 8a^2 - 38a + 7.
Learn more about Multiplying polynomials