We must change g(x) into f(x) in order to find f(g(x)).
Since g(x)=3x+7 and f(x)=4x+5, let’s replace
f(g(x))=f(3x+7)
Now, replace x in f(x)=4x+5 with 3x+7:
f(g(x))=4(3x+7)+5
Give out the four:
f(g(x))=12x+28+5
Put similar terms together:
f(g(x))=12x+33
Therefore, choice (B) is the right one.
We must change g(x) into f(x) in order to find f(g(x)).
Since g(x)=3x+7 and f(x)=4x+5, let’s replace
f(g(x))=f(3x+7)
Now, replace x in f(x)=4x+5 with 3x+7:
f(g(x))=4(3x+7)+5
Give out the four:
f(g(x))=12x+28+5
Put similar terms together:
f(g(x))=12x+33
Therefore, choice (B) is the right one.