For example, you may have gotten rid of a denominator some time in trying to find a solution. But if the denominator had a variable, then it’s possible for the denominator to equal zero when you check. This would then prove that the solution is in fact NOT a solution.

I’ll try to find an example of this for you.

Example… if you were to work thru this problem:

1+(3x)/(x+2)=-6(x+2)

you would get x=-2, but it cannot be, as that would create zeroes the denominators above, so that equation has no solution.

There are other examples where you will have two answers, but you have to throw one out for the above reason.