This came about when I was trying to convert 1/(1-x^2/2) to normal form, i.e. tell Mathematica to change the above to 1+x^2/2 But doing Simplify[1/(1-x^2/2)] or Expand does not work. So the only solution I found is to use Series command, as follows
Normal[Series[1/r, {x, 0, 2}]] Out[189]= 1 + x^2/2