Question

Write the inverse function for the function, ƒ(x) =1/2x + 4. Then, find the value of ƒ^ -1(4). Type your answers in the box.

Answer 1

Answer:

f⁻¹(x) = 2x - 8

f⁻¹(4) = 2 × 4 - 8

f⁻¹(4) = 0

Step-by-step explanation:

$f(x) = \frac{1}{2} x + 4\\x = \frac{1}{2} f^{-1}(x) + 4\\x - 4 = \frac{1}{2} f^{-1}(x)\\2x - 8 = f^{-1}(x)\\f^{-1}(x) = 2x - 8$

Let's test it

$f^{-1}(f(x)) = 2(f(x)) - 8\\f^{-1}(f(x)) = 2( \frac{1}{2}x + 4) - 8\\f^{-1}(f(x)) = \frac{2}{2}x + 8 - 8\\f^{-1}(f(x)) = x$

So we do indeed have the inverse function, so using that we can plug in the values requested:

f⁻¹(x) = 2x - 8

f⁻¹(4) = 2 × 4 - 8

f⁻¹(4) = 0