[size=3]A = B[/size]
[size=3]A² = AB[/size]
[size=3]A²-B² = AB - B²[/size]
[size=3](A+B)(A-B) =B(A-B)[/size]
[size=3](A+B) =B[/size]
[size=3]A+A =A[/size]
[size=3]2A[/size][size=3] =A[/size]
[size=3][/size]
[size=3]2 =1[/size]