let c, d be Real; :: thesis: ( c > 0 implies (|.d.| + c) + 1 <> - (((|.d.| + c) + c) + d) )
assume A1: c > 0 ; :: thesis: (|.d.| + c) + 1 <> - (((|.d.| + c) + c) + d)
assume A2: (|.d.| + c) + 1 = - (((|.d.| + c) + c) + d) ; :: thesis: contradiction
per cases ( d >= 0 or d < 0 ) ;
end;