Explanation:
We are given two functions:
[tex]\begin{gathered} f(x)=-2x+7 \\ g(x)=-6x+3 \end{gathered}[/tex]The question wants us to obtain f.g and its's domain
To do so,
Let us first obtain f.g
[tex]fg=f(x)\times g(x)=\mleft(-2x+7\mright)\times(-6x+3)=12x^2-48x+21[/tex]Next, we will find its domain
We can use the graph below to help
The domain of f.g is
[tex]\begin{bmatrix}\mathrm{Solution\colon}\: & \: -\infty\: Therefore[tex]\text{The domain is all real numbers}[/tex]Hence
The answer is the second option
[tex]12x^2-48x+21;\text{ All real numbers}[/tex]