A=B
A[squared]=AB forgot parenthesis around AB
A[squared + B[squared]=AB - B[squared]
(A+B) (A-B) + (A-B)B
A+B=B
B+B=B
2B=B
2=1

2=2
2^2=(2*2)
2^2 + 2^2=(2*2) - B (where did that B come from?)


also you cant just change a to b whenever you want it just doesnt work when you're using variables or even representative terms like 'A' and 'B' because it allows you to manipulate it and combine/extrapolate more terms when you cant do it with real numbers. Numbers have to retain their identity even when they are equal. its the law ok