pre calc question

Question

f(x)= x+4/x+6

f^-1(-3)=

Answer 1

If f(a) = b, then f^-1(b) = a

First find x so that f(x) = -3:

(x+4) / (x+6) = -3

x+4 = -3x - 18

4x = -22

x = -5.5

Since f(-5.5) = -3, f^-1(-3) - -5.5