f(x)=2x-1/x+5 maka f-¹(4)=

f(x) = (2x - 1) / (x + 5)
y(x + 5) = 2x - 1
yx + 5y = 2x - 1
yx - 2x = -5y - 1
x (y - 2) = (-5y - 1)
x = (-5y - 1) / (y - 2)
f-¹(x) = (-5x - 1) / (x - 2)

f-¹(4) = (-5 (4) - 1) / (4 - 2)
= (-21) / 2
= -21/2

f(x) = 2x-1/x+5
maka,   y = (2x-1)/x+5
             y = (2x-1+5x)x
           xy = 2x-1+5x
 xy-2x-5x = -1
      x(y-7) = -1
            x = -1/(y-7)
f invers (y) = -1/(y-7)
f invers (x) = -1/(x-7)
f invers (4) = -1/(4-7)
                  = -1/-3
                  = 1/3