My youngest brother had a pre-algebra test yesterday and he was asked to tell if two expressions are equal or not.
We agreed on most of the things but on this one I find it hard to make him accept my answer. He was asked to tell if $8a\cdot4a [\space\space\space\space\space\space\space\space] 64a$ are equal or not. He checked for a specific case (one of the only 2 cases where this equation is true) and showed that for $a = 2$ the equation stands, and I find it hard to make him agree with me that if the equation stands only for $a = 0,2$ than the two expression are equal for those $a$'s only and thus the expression can't be called equal.
I think I'm having a hard time explaining him the definition of equality with variables, and here's where you enter the picture.