ANSWER
[tex]\begin{gathered} f(6)=-40 \\ x=+4;x=-4 \end{gathered}[/tex]EXPLANATION
We have that:
[tex]\begin{gathered} f(x)=-9x+14 \\ g(x)=-3x^2 \end{gathered}[/tex]To find the value of f(6), we have to substitute 6 into f(x). That is:
[tex]\begin{gathered} f(6)=-9(6)+14 \\ f(6)=-54+14 \\ f(6)=-40 \end{gathered}[/tex]That is the value of f(6).
To find the values of x when g(x) =-48, we have to substitute -48 for g(x) in the function and solve for x:
[tex]\begin{gathered} -48=-3x^2 \\ \Rightarrow x^2=\frac{-48}{-3} \\ x^2=16 \\ \Rightarrow x=\pm\sqrt[]{16} \\ x=+4;x=-4 \end{gathered}[/tex]Those are the values of x for g(x) = -48
