If f:1,∞→2,∞ is given by fx=x+1x then f-1x equals

f:1,∞→2,∞            fx=x+1x=yor        x2-yx+1=0or        x=y±y2-42But   given   f:1,∞→2,∞  ∴       x=y+y2-42or       f-1x=x+x2-42