y=4x+3
4x=y-3
∴x=y/4-3/4
∴反函数是y=x/4 -3/4
y=(x+1)/(x-1)
y(x-1)=x+1
xy-y=x+1
xy-x=y+1
x(y-1)=y+1
x=(y+1)/(y-1)
∴反函数是y=(x+1)/(x-1) x≠1