Answer :
[tex](f-g)(3t) \\ \\ f(x)-g(x) \\ \\ f(3t)-g(3t) \\ \\ ((3t)^2+1)-((3t)-4) \\ \\ 9t^2+1-3t+4 \\ \\ 9t^2-3t+5[/tex]
f(x)=x²+1
g(x)=x-4
------------
f(x)-g(x)
=x²+1-(x-4)
=x²+1-x+4
=x²-x+5
------------
Therefore:
(f-g)(3t)
=(3t)²-3t+5
=3²t²-3t+5
=9t²-3t+5
g(x)=x-4
------------
f(x)-g(x)
=x²+1-(x-4)
=x²+1-x+4
=x²-x+5
------------
Therefore:
(f-g)(3t)
=(3t)²-3t+5
=3²t²-3t+5
=9t²-3t+5