If f of x and f inverse of x are inverse functions of each other and f of x is equal to 2 x plus 5 , what is f inverse of 8 ?
Answer
A
3 halves
B
23
C
negative 1
D
41 eighths
Explanation
To find f inverse of 8, solve f(x) = 8. Since f(x) = 2x + 5, we get 2x + 5 = 8, so 2x = 3 and x = 3/2. Therefore, f inverse of 8 is 3/2, or three halves.
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