Inverse Function Example 4


Question:
(a) If f : xx – 2, find f -1 (5),
(b) if f:x x+9 x5 , x5, find  f 1 (3).  

Solution:
(a)
f (x) = x – 2
Let y = f -1 (5)
f (y) = 5
y – 2 = 5
y = 7
therefore, f -1 (5) = 7

(b)
f(x)= x+9 x5 Let y= f 1 (3) f(y)=3 y+9 y5 =3 y+9=3y15 2y=24 y=12 f 1 ( 3 )=7