Question

Use the function to answer the question.

f(x) = 4x - 8
what is the value of f^-1(-2)?

please explain

Answer 1

So plug in, (-2) into the x's in the function above. Multiply 4 times -2 and you get.. then you subtract -8 and 8 and the answer is...?

Answer 2

-16??

Answer 3

Exactly!

Answer 4

my teacher says thats wrong though

Answer 5

first find f inverse

\(\large\tt \color{black}{f(x) = 4x - 8}\)

\(\large\tt \color{black}{y = 4x - 8}\)


\(\large\tt \color{black}{y +8= 4x}\)

\(\large\tt \color{black}{\dfrac{y +8}{4}= x}\)

swap x with y


\(\large\tt \color{black}{\dfrac{x+8}{4}= y}\)


\(\large\tt \color{black}{f^{-1}(x) = \dfrac{x+8}{4}}\)


\(\large\tt \color{black}{f^{-1}(-2) = \dfrac{-2+8}{4}}\)


\(\large\tt \color{black}{f^{-1}(-2) = \dfrac{6}{4}}\)


\(\large\tt \color{black}{f^{-1}(-2) = \dfrac{3}{2}}\)

Answer 6

thank you @mathmath333

Answer 7

welcome