4 The figure above shows the graph of the function f defined

4. The figure above shows the graph of the function f defined f(x) V2x+4. If f is the inverse function of f, what is the value of f (2)? (A) 8 (B) -2 (C) 0 (D) (E) V8

Solution

f(x) =y = sqrt(2x+4)

find f^-1(x) by plugging x=y and y=x and solve for x:

y = sqrt(2x +4)

x = sqrt(2y +4)

(x^2 -4)/2 = y

f^-1(x) = (x^2 -4)/2

f^-1(2) = (4 -4)/2 =0

Option C