Answer: a. -3(x+1), b. 19-3x, c. -9 and d. 13
Step-by-step explanation:
Lets begin with a. (fog)(x)=f(g(x))
=f(2x+x+7), Note that 2x+x+7=3x+7
=f(3x+7) (where there is x if the function f(x) we
substitute x by 3x+7)
=4-(3x+7) =4-3x-7=-3x-3= -3(x+1).
b. (gof)(x)=g(f(x))=g(4-x) (where there is x in the function
g(x) we substitute with 4-x)
= 3(4-x)+7 = 19-3x
c. (fog)(2) = -3(2+1) = -9 (we now substitute x with 2 in -3(x+1). )
d. (gof)(2) = 19-3(2)=19-6=13. (Again we now substitute x with
2 in 19-3x)
