diketahui f(x)=x/x-1, maka f^-1(3) adalah

y=x/x-1
x/x-1=y
x=y(x-1)
x=yx-y
-yx+x=-y
x(-y+1)=-y
x=-y/-y+1

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