College

Let [tex]f(x)=9x^4[/tex] and [tex]g(x)=5-2x[/tex]. Evaluate [tex]f(x) \cdot g(x)[/tex].

A. [tex]f(x) \cdot g(x) = 45x^4 - 18x^5[/tex]

B. [tex]f(x) \cdot g(x) = 45x^5 - 9x^4 - 2x[/tex]

C. [tex]f(x) \cdot g(x) = 45 + 5x^4 - 18x[/tex]

D. [tex]f(x) \cdot g(x) = -18x^4 + 45x^5[/tex]

Answer :

We are given the functions
[tex]$$f(x)=9x^4 \quad \text{and} \quad g(x)=5-2x.$$[/tex]
To find the product, we multiply these two functions:

1. Write the product:
[tex]$$f(x) \cdot g(x) = 9x^4 \cdot (5-2x).$$[/tex]

2. Distribute the multiplication over the terms inside the parentheses:
[tex]$$f(x) \cdot g(x) = 9x^4\cdot5 + 9x^4\cdot(-2x).$$[/tex]

3. Multiply each term:
- For the first term:
[tex]$$9x^4\cdot5 = 45x^4.$$[/tex]
- For the second term:
[tex]$$9x^4\cdot(-2x) = -18x^5.$$[/tex]

4. Combine the results:
[tex]$$f(x) \cdot g(x) = 45x^4 - 18x^5.$$[/tex]

This product corresponds to option A:

[tex]$$\textbf{A } \; f(x) \cdot g(x)=45 x^4-18 x^5.$$[/tex]