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**rgragsda** For example, the study book I'm using said that if you're trying to find "1/a= 1/b + 1/c," you can't just take the reciprocal of both sides, i.e., it's not just a= b +c, but first must add "1/b" and "1/c" to get (b+c/bc)= 1/a, and then you can take the reciprocal to get a=bc/b+c. OR for (1/a-b)=5, just take the reciprocal to find a-b=1/5, so a=b+1/5. So my question is, what is the general rule about when it is ok to take the reciprocal of both sides of the equation? what are the conditions?