Question

Let f(x) = 4x-5 and g(x) = 3x, find (fg)(x).

Answer 1

I believe you mean "find f(g(x))"
g(x) is defined as 3x
Now the problem is simplified to f(3x)
Next, plug in 3x into the f(x) equation
4(3x)-5
12x-5
f(g(x)) = 12x-5

Answer 2

`(fg)(x)= 12x^2- 15x`

Explanation:

`f(x)= 4x-5`

`g(x)= 3x`

Fidn (fg)(x) = f(x) times g(x)

WE multiply f(x) and g(x)

`(fg)(x)= f(x) \cdot g(x)= (4x-5)(3x)`

Multiply 3x inside the parenthesis

`(fg)(x)= f(x) \cdot g(x)= (4x-5)(3x)=12x^2-15x`

So
`(fg)(x)= 12x^2- 15x`