Final answer:
To find (a*b)(x), we need to multiply the two polynomials a(x) and b(x) using the distributive property. The resulting polynomial is x^3 + 9x^2 + 20x.
Step-by-step explanation:
To find (a*b)(x), we need to multiply the two polynomials a(x) and b(x). Let's substitute the given expressions for a(x) and b(x) into the expression:
(a*b)(x) = (x+4)(x^2+5x)
To simplify this expression, we can use the distributive property to multiply each term in the first polynomial by each term in the second polynomial:
(a*b)(x) = x(x^2+5x) + 4(x^2+5x)
Next, we can simplify each term:
(a*b)(x) = x^3 + 5x^2 + 4x^2 + 20x
Combining like terms, we get the final simplified polynomial:
(a*b)(x) = x^3 + 9x^2 + 20x