An equation is two expressions that are set equal to each other. Conditional equations, identities, and not equations. A Conditional equation is such that its truth is dependent on which number x stands for. For example 2x+1=5 is only true when x = 2. An Identity is when both sides are exactly the same so 3n+1=3n+1 because when we simplify we get 0=0. x-3 and 2/x +1= 2/x +2 are not equations simply because they do not equal anything or are false.