# How to control pre-simplify (Part 1) [duplicate]

For example, if you enter

Reduce [x ^ 2 == x ^ 2 / x, x]


The output is

x == 0 || x == 1

Well, the correct answer is x == 1. Although this is a trivial example, is there no possibility that similar errors will occur in the process of internal calculation?

## marked as duplicate by m_goldberg, bbgodfrey, jkuczm, mikado, J. M. will be back soon♦Jul 30 '17 at 15:28

• Note that entering x ^ 2 == x ^ 2 / x directly automagically performs the cancellation. In any event, read up on the case of "generically correct" solutions. – J. M. will be back soon Jul 30 '17 at 8:23
• The answer Reduce gave you is entirely correct. The quadratic form x(x - 1) has roots at 0 and1. – m_goldberg Jul 30 '17 at 8:50
• You could use my RestrictDomain function: Reduce[RestrictDomain[x^2 == x^2/x, x, Complexes], x] (* x == 1 *). – jkuczm Jul 30 '17 at 12:47