looks like a neat math trick.... with a hidden error

let A=1, B=1
A^2=B^2 because A=B, so
A^2=AB and
A^2-B^2=A^2-AB , next we factor
(A+B)(A-B)=A(A-B) , divide like terms
(A+B)=A
substituting our variables for their values we learn that
2=1.