Why?! 2=1

a= b 

           2        2     

      a    =  b 

         2        2           2        2     

    a     -  b    =    b   -    b 

 ( a - b ) ( a+ b ) = b ( b - b ) 

                                             ( a - b ) ( a + b ) = b ( a - b )
                                                                  a + b ) = b )

                                                                     b + b = b
                                                                        2b = b
                                                                        1  =  2