# Self Inverse in Integral Domains [duplicate]

I need to show that if R is an integral domain and it has unity then the only elements of R which are inverse to itself are 1 and -1 (with respect to multiplication). But I don't know where to start. Can anyone help? Thanks..

• Write it in the form of an equation rather than in the form of an English phrase. – user14972 May 12 '13 at 21:30
• More generally, any polynomial has number of roots bounded by its degree. – anon May 12 '13 at 21:49

Here's a hint: $$(x+1)(x-1)=x^2-1.$$