23
QuizMultiple Choice

Analyzing Compositions of Functions — Quiz

Question 23 • Mathematics III

If f of x is equal to the fraction with numerator x minus 1 and denominator 3 and g of x is equal to 3 x plus 1 , what is open paren f circ g close paren times x ?

Answer
A
open paren f circ g close paren times x is equal to x minus 3
B
open paren f circ g close paren times x is equal to 3 x
C
open paren f circ g close paren times x is equal to 3 x plus 1
D
open paren f circ g close paren times x is equal to x

Explanation

Composition means apply g first, then substitute its output into f. Since g(x) = 3x + 1 and f(x) = (x − 1)/3, we get f(g(x)) = ((3x + 1) − 1)/3 = 3x/3 = x. Therefore, the correct choice is “(f ∘ g)(x) = x.”

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