Question

If f(x)=2x+1/x-4, what is the value of f^-1(3)?

Answer 1

D. 13.

Explanation:

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

let y = 2x + 1 / x - 4

xy - 4y = 2x + 1

xy - 2x = 4y + 1

x(y - 2) = 4y + 1

x = (4y + 1)/(y - 2)

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

and f^-1(3) = (4(3) + 1) / (3 - 2)

= 13/1

= 13.