Question

can anyone help?....

Answer 1

The answer two this question is C.

You can get this answer by multiplying the two polynomials and then simplifying. See the steps below:
(4x^2 - 5)(x + 3) ---> Now multiply the two parenthesis. 
4x^3 - 5x + 12x^2 - 15 ---> Arrange the numbers by decreasing  exponents. 
4x^3 + 12x^2 - 5x - 15

No simplifying can be done since there are no like terms.

Answer 2

Answer: $fg(x)=4x^3+12x^2-5x-15$

Step-by-step explanation:

Given: $f(x)=4x^2-5\text{ and } g(x)=x+3$

We know that for any function f(x) and g(x), the multiplication function (fg) (x) is given by :-

$fg(x)=f(x)g(x)$

Now, for the given functions, we have

$fg(x)=(4x^2-5)(x+3)\\\\\Rightarrow\ fg(x)=4x^2(x+3)-5(x+3)\\\\\Rightarrow\ fg(x)=4x^3+12x^2-5x-15$