We have to be careful here!  We might be tempted
to use the zero-factor principle. However that 
will lead us astray because  is not 
defined at ANY of the values of x for which
!

So do NOT do this:



Instead use the identity  to replace .




We can cancel 's as long as we are careful 
not to allow any values of x which cause the 
denominator  to be zero.

 

That leaves:



which has solution 

, where n is any integer.

And this is a valid solution since 
is always either  or , and never .

Edwin