Question

if f(x) = 3x+2, find f(f^-1(14))?

a) 44

b) 176

c) 4

d) 14

Answer 1

$f(x)=3x+2\\\\y=3x+2\ \ \ |-2\\\\3x=y-2\ \ \ \ |:3\\\\x=\dfrac{y-2}{3}\to f^{-1}(x)=\dfrac{x-2}{3}$

$f^{-1}(14)=\dfrac{14-2}{3}=\dfrac{12}{3}=4$
$f(f^{-1}(14))=3\cdot4+2=12+2=14$

Answer: d) 14